Cisco Security Advisory

Cisco IOS Software Reverse SSH Denial of Service Vulnerability

Advisory ID: cisco-sa-20120328-ssh

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120328-ssh

Revision 1.0

For Public Release 2012 March 28 16:00  UTC (GMT)


Summary

The Secure Shell (SSH) server implementation in Cisco IOS Software and Cisco IOS XE Software contains a denial of service (DoS) vulnerability in the SSH version 2 (SSHv2) feature. An unauthenticated, remote attacker could exploit this vulnerability by attempting a reverse SSH login with a crafted username.  Successful exploitation of this vulnerability could allow an attacker to create a DoS condition by causing the device to reload.  Repeated exploits could create a sustained DoS condition.

The SSH server in Cisco IOS Software and Cisco IOS XE Software is an optional service, but its use is highly recommended as a security best practice for the management of Cisco IOS devices.  Devices that are not configured to accept SSHv2 connections are not affected by this vulnerability.

Cisco has released free software updates that address this vulnerability.  This advisory is available at the following link: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120328-ssh

Note: The March 28, 2012, Cisco IOS Software Security Advisory bundled publication includes nine Cisco Security Advisories. Each advisory lists the Cisco IOS Software releases that correct the vulnerability or vulnerabilities detailed in the advisory as well as the Cisco IOS Software releases that correct all vulnerabilities in the March 2012 bundled publication.

Individual publication links are in "Cisco Event Response: Semi-Annual Cisco IOS Software Security Advisory Bundled Publication" at the following link:

http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_mar12.html


Affected Products


Vulnerable Products

Cisco devices that are running affected Cisco IOS Software or Cisco IOS XE Software versions are vulnerable when they have the SSH server enabled and allow SSHv2 logins.  Only SSHv2 is affected.

To determine if SSH is enabled, use the show ip ssh command.  
  Router#show ip ssh 
  SSH Enabled - version 2.0 
  Authentication timeout: 120 secs; Authentication retries: 3
The previous output shows that SSH is enabled on this device and that the SSH protocol major version that is being supported is 2.0. Possible values for the SSH protocol versions that are reported by Cisco IOS are: 
  • 1.5: only SSH protocol version 1 is enabled 
  • 1.99: SSH protocol version 2 with SSH protocol version 1 compatibility enabled 
  • 2.0: only SSH protocol version 2 is enabled 
The SSH server is not available in all IOS images. If the show ip ssh command is not available, the device is not vulnerable. Devices that do not support SSHv2 are not vulnerable.

To determine the Cisco IOS Software release that is running on a Cisco product, administrators can log in to the device and issue the show version command to display the system banner. The system banner confirms that the device is running Cisco IOS Software by displaying text similar to "Cisco Internetwork Operating System Software" or "Cisco IOS Software." The image name displays in parentheses, followed by "Version" and the Cisco IOS Software release name. Other Cisco devices do not have the show version command or may provide different output.

The following example identifies a Cisco product that is running Cisco IOS Software Release 15.0(1)M1 with an installed image name of C3900-UNIVERSALK9-M:

Router> show version 
Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), Version 15.0(1)M1, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Wed 02-Dec-09 17:17 by prod_rel_team
!--- output truncated 

Additional information about Cisco IOS Software release naming conventions is available in "White Paper: Cisco IOS and NX-OS Software Reference Guide" at http://www.cisco.com/web/about/security/intelligence/ios-ref.html.


Products Confirmed Not Vulnerable

Cisco IOS-XR is not affected by this vulnerability.

No other Cisco products are currently known to be affected by this vulnerability.

Details

Secure Shell (SSH) is a protocol which provides a secure remote access connection to network devices. 

The SSH server implementation in Cisco IOS Software and Cisco IOS XE Software contains a DoS vulnerability in the SSH version 2 (SSHv2) feature that could allow an unauthenticated remote attacker to cause a device to reload.  An attacker could exploit this vulnerability by attempting a reverse SSH login with a crafted username.  Successful exploitation of this vulnerability could allow an attacker to create a DoS condition by causing the device to reload.  Repeated exploits could create a sustained DoS condition.

The SSH server in Cisco IOS Software and Cisco IOS XE Software is an optional service, but its use is highly recommended as a security best practice for management of Cisco IOS devices. SSH can be configured as part of the AutoSecure feature in the initial configuration of IOS devices, AutoSecure run after initial configuration, or manually. SSH is enabled any time RSA keys are generated such as when an http secure-server or trust points for digital certificates are configured.  Devices that are not configured to accept SSHv2 connections are not affected by this vulnerability.

A complete TCP three-way handshake is required to exploit this vulnerability.  Reverse SSH traffic uses TCP port 22 by default.

This vulnerability has been documented in Cisco Bug ID CSCtr49064 and has been assigned the Common Vulnerabilities and Exposures (CVE) ID CVE-2012-0386.

Vulnerability Scoring Details

Cisco has scored the vulnerability in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this security advisory is in accordance with CVSS version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability severity and helps organizations determine the urgency and priority of a response.

Cisco has provided a base and temporal score. Customers can also compute environmental scores that help determine the impact of the vulnerability in their own networks.

Cisco has provided additional information regarding CVSS at the following link:

http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html

Cisco has also provided a CVSS calculator to compute the environmental impact for individual networks at the following link:

http://intellishield.cisco.com/security/alertmanager/cvss


CSCtr49064 - Cisco IOS Software Reverse SSH Denial of Service Vulnerability

Calculate the environmental score of CSCtr49064

CVSS Base Score - 7.8

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

Impact

Successful exploitation of this vulnerability could allow an unauthenticated, remote attacker to create a DoS condition by causing the device to reload.  Repeated exploits could create a sustained DoS condition.

Software Versions and Fixes

When considering software upgrades, customers are advised to consult the Cisco Security Advisories and Responses archive at http://www.cisco.com/go/psirt and review subsequent advisories to determine exposure and a complete upgrade solution.

In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

Cisco IOS Software

Each row of the following Cisco IOS Software table corresponds to a Cisco IOS Software train. If a particular train is vulnerable, the earliest releases that contain the fix are listed in the First Fixed Release column. The First Fixed Release for All Advisories in the March 2012 Bundled Publication column lists the earliest possible releases that correct all the published vulnerabilities in the Cisco IOS Software Security Advisory bundled publication. Cisco recommends upgrading to the latest available release, where possible.

The Cisco IOS Software Checker allows customers to search for Cisco Security Advisories that address specific Cisco IOS Software releases. This tool is available on the Cisco Security Intelligence Operations (SIO) portal at http://tools.cisco.com/security/center/selectIOSVersion.x

Major Release      Availability of Repaired Releases
Affected 12.0-Based Releases First Fixed Release First Fixed Release for All Advisories in the March 2012 Cisco IOS Software Security Advisory Bundled Publication
There are no affected 12.0 based releases
Affected 12.2-Based Releases First Fixed Release First Fixed Release for All Advisories in the March 2012 Cisco IOS Software Security Advisory Bundled Publication
12.2 Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2B Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2BC Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2BW Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2BX Not vulnerable
Vulnerable; First fixed in Release 12.2SB
12.2BY Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2BZ Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2CX Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2CY Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2CZ Not vulnerable
Vulnerable; First fixed in Release 12.0S
12.2DA Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2DD Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2DX Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2EU Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2EW Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2EWA Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2EX Vulnerable; First fixed in Release 15.0SE
Releases up to and including 12.2(55)EX3 are not vulnerable.
Vulnerable; First fixed in Release 15.0SE
12.2EY 12.2(58)EY2
12.2(52)EY4
12.2EZ Not vulnerable
Vulnerable; First fixed in Release 15.0SE
12.2FX Not vulnerable
Vulnerable; First fixed in Release 15.0SE
12.2FY Not vulnerable
Vulnerable; First fixed in Release 15.0SE
12.2FZ Not vulnerable
Vulnerable; First fixed in Release 15.0SE
12.2IRA Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2IRB Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2IRC Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2IRD Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2IRE Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2IRF Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2IRG Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2IRH Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2IXA Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2IXB Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2IXC Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2IXD Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2IXE Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2IXF Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2IXG Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2IXH Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2JA Not vulnerable
Not vulnerable
12.2JK Not vulnerable
Not vulnerable
12.2MB Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2MC Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2MRA Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2MRB Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2S Not vulnerable
Releases prior to 12.2(30)S are vulnerable; Releases 12.2(30)S and later are not vulnerable. First fixed in Release 12.0S
12.2SB Not vulnerable
12.2(33)SB12
12.2SBC Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2SCA Not vulnerable
Vulnerable; First fixed in Release 12.2SCE
12.2SCB Not vulnerable
Vulnerable; First fixed in Release 12.2SCE
12.2SCC Not vulnerable
Vulnerable; First fixed in Release 12.2SCE
12.2SCD Not vulnerable
Vulnerable; First fixed in Release 12.2SCE
12.2SCE Not vulnerable
12.2(33)SCE6
12.2SCF Not vulnerable
12.2(33)SCF2
12.2SE Vulnerable; First fixed in Release 15.0SE
Releases up to and including 12.2(58)SE1 are not vulnerable.

12.2(55)SE5 *
12.2SEA Not vulnerable
Vulnerable; First fixed in Release 15.0SE
12.2SEB Not vulnerable
Vulnerable; First fixed in Release 15.0SE
12.2SEC Not vulnerable
Vulnerable; First fixed in Release 15.0SE
12.2SED Not vulnerable
Vulnerable; First fixed in Release 15.0SE
12.2SEE Not vulnerable
Vulnerable; First fixed in Release 15.0SE
12.2SEF Not vulnerable
Vulnerable; First fixed in Release 15.0SE
12.2SEG Not vulnerable
Vulnerable; First fixed in Release 15.0SE
12.2SG Not vulnerable
12.2(53)SG7; Available on 07-MAY-12
12.2SGA Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SL Not vulnerable
Not vulnerable
12.2SM Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SO Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SQ Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SRA Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2SRB Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2SRC Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2SRD Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2SRE Not vulnerable
12.2(33)SRE6
12.2STE Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SU Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2SV Not vulnerable
Releases up to and including 12.2(18)SV2 are not vulnerable.
12.2SVA Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SVC Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SVD Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SVE Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SW Not vulnerable
Vulnerable; First fixed in Release 12.4T
12.2SX Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SXA Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SXB Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SXD Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SXE Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SXF Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SXH Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2SXI Not vulnerable
12.2(33)SXI9
12.2SXJ Not vulnerable
12.2(33)SXJ2
12.2SY Not vulnerable
12.2(50)SY2; Available on 11-JUN-12
12.2SZ Not vulnerable
Vulnerable; First fixed in Release 12.0S
12.2T Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2TPC Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2XA Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XB Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XC Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XD Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XE Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XF Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XG Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XH Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XI Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XJ Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XK Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XL Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XM Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XNA Please see Cisco IOS-XE Software Availability
Please see Cisco IOS-XE Software Availability
12.2XNB Please see Cisco IOS-XE Software Availability
Please see Cisco IOS-XE Software Availability
12.2XNC Please see Cisco IOS-XE Software Availability
Please see Cisco IOS-XE Software Availability
12.2XND Please see Cisco IOS-XE Software Availability
Please see Cisco IOS-XE Software Availability
12.2XNE Please see Cisco IOS-XE Software Availability
Please see Cisco IOS-XE Software Availability
12.2XNF Please see Cisco IOS-XE Software Availability
Please see Cisco IOS-XE Software Availability
12.2XO Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2XQ Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XR Not vulnerable
Releases prior to 12.2(15)XR are vulnerable; Releases 12.2(15)XR and later are not vulnerable. First fixed in Release 15.0M
12.2XS Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XT Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XU Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XV Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2XW Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2YA Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2YC Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2YD Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2YE Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2YK Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2YO Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2YP Not vulnerable
Vulnerable; First fixed in Release 15.0M
Releases up to and including 12.2(8)YP are not vulnerable.
12.2YT Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2YW Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2YX Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2YY Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2YZ Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2ZA Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2ZB Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2ZC Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2ZD Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2ZE Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2ZH Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.2ZJ Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2ZP Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2ZU Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2ZX Not vulnerable
Vulnerable; First fixed in Release 12.2SRE
12.2ZY Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.2ZYA Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Affected 12.3-Based Releases First Fixed Release First Fixed Release for All Advisories in the March 2012 Cisco IOS Software Security Advisory Bundled Publication
There are no affected 12.3 based releases
Affected 12.4-Based Releases First Fixed Release First Fixed Release for All Advisories in the March 2012 Cisco IOS Software Security Advisory Bundled Publication
12.4 Releases 12.4(13d) and prior are not vulnerable; first fixed in 12.4(25f)
Vulnerable; First fixed in Release 15.0M
12.4GC Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4JA 12.4(23c)JA4
12.4(25e)JA
12.4(23c)JA4
12.4(25e)JA
12.4JAX Vulnerable; First fixed in Release 12.4JA
Vulnerable; First fixed in Release 12.4JA
12.4JDA Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4JDC Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4JDD Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4JDE Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4JHA Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4JHB Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4JHC Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4JK Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4JL Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4JX Vulnerable; First fixed in Release 12.4JA
Releases up to and including 12.4(3g)JX2 are not vulnerable.
Vulnerable; First fixed in Release 12.4JA
12.4JY Vulnerable; First fixed in Release 12.4JA
Vulnerable; First fixed in Release 12.4JA
12.4JZ Vulnerable; First fixed in Release 12.4JA
Vulnerable; First fixed in Release 12.4JA
12.4MD 12.4(22)MD3; Available on 30-MAR-12
12.4(22)MD3; Available on 30-MAR-12
12.4MDA 12.4(24)MDA11
12.4(24)MDA11
12.4MDB 12.4(24)MDB5a
12.4(24)MDB5a
12.4MDC Not vulnerable
Not vulnerable
12.4MR Releases up to and including 12.4(16)MR1 are not vulnerable.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4MRA Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4MRB Vulnerable; First fixed in Release 12.4T
Vulnerable; First fixed in Release 15.0M
12.4SW Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4T 12.4(15)T16
12.4(24)T6

12.4(15)T17
12.4(24)T7

12.4XA Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XB Not vulnerable
Vulnerable; First fixed in Release 12.4T
12.4XC Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XD Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XE Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XF Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XG Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XJ Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XK Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XL Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4XM Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XN Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4XP Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4XQ Vulnerable; First fixed in Release 12.4T
Vulnerable; First fixed in Release 15.0M
12.4XR Vulnerable; First fixed in Release 12.4T
Vulnerable; First fixed in Release 12.4T
12.4XT Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XV Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4XW Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XY Not vulnerable
Vulnerable; First fixed in Release 15.0M
12.4XZ Vulnerable; First fixed in Release 12.4T
Vulnerable; First fixed in Release 15.0M
12.4YA Vulnerable; First fixed in Release 12.4T
Vulnerable; First fixed in Release 15.0M
12.4YB Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4YD Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
12.4YE 12.4(24)YE3d
12.4(24)YE3d
12.4YG 12.4(24)YG4
12.4(24)YG4
Affected 15.0-Based Releases First Fixed Release First Fixed Release for All Advisories in the March 2012 Cisco IOS Software Security Advisory Bundled Publication
15.0M 15.0(1)M7
15.0(1)M8
15.0MR Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
15.0MRA Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
15.0S 15.0(1)S5
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.0(1)S5
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.0SA Not vulnerable
Not vulnerable
15.0SE 15.0(1)SE1
15.0(2)SE; Available on 06-AUG-12
15.0(1)SE1
15.0SG Not vulnerable
Cisco IOS XE devices: Please see Cisco IOS-XE Software Availability
15.0(2)SG2
Cisco IOS XE devices: Please see Cisco IOS-XE Software Availability
15.0SY Not vulnerable
15.0(1)SY1
15.0XA Vulnerable; First fixed in Release 15.1T
Vulnerable; First fixed in Release 15.1T
15.0XO Cisco IOS XE devices: Please see Cisco IOS-XE Software Availability
Cisco IOS XE devices: Please see Cisco IOS-XE Software Availability
Affected 15.1-Based Releases First Fixed Release First Fixed Release for All Advisories in the March 2012 Cisco IOS Software Security Advisory Bundled Publication
15.1EY 15.1(2)EY1a
15.1(2)EY2
15.1GC 15.1(2)GC2
15.1(2)GC2
15.1M 15.1(4)M2

15.1(4)M4; Available on 30-MAR-12
15.1MR 15.1(1)MR3
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
15.1S 15.1(3)S2
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.1(3)S2
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.1SG Not vulnerable
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
Not vulnerable
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.1SNG Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
15.1SNH Not vulnerable
Not vulnerable
15.1T 15.1(1)T4
15.1(2)T5; Available on 27-APR-12
15.1(3)T3
15.1(3)T3
15.1XB Vulnerable; First fixed in Release 15.1T
Vulnerable; First fixed in Release 15.1T
Affected 15.2-Based Releases First Fixed Release First Fixed Release for All Advisories in the March 2012 Cisco IOS Software Security Advisory Bundled Publication
15.2GC 15.2(1)GC1
15.2(1)GC2
15.2S Not vulnerable
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.2(1)S1
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability

15.2T 15.2(1)T2
15.2(2)T
15.2(2)T1
15.2(1)T2
15.2(2)T1
15.2(3)T; Available on 30-MAR-12

* Cisco Catalyst 3550 Series Switches support the Internet Key Exchange (IKE) feature and are vulnerable to Cisco bug ID CSCts38429 when the devices are running Layer 3 images; however, this product reached the End of Software Maintenance milestone.  Cisco 3550 Series SMI Switches that are running Layer 2 images do not support IKE and are not vulnerable.  No other Cisco devices that run 12.2SE-based software are vulnerable.

Cisco IOS XE Software

Cisco IOS XE Software is affected by the vulnerability that is disclosed in this document.

Cisco IOS XE Software Release First Fixed Release First Fixed Release for All Advisories in the March 2012 Cisco IOS Software Security Advisory Bundled Publication
2.1.x Not vulnerable Vulnerable; migrate to 3.4.2S or later.
2.2.x Not vulnerable Vulnerable; migrate to 3.4.2S or later.
2.3.x Vulnerable; migrate to 3.4.2S or later. Vulnerable; migrate to 3.4.2S or later.
2.4.x Vulnerable; migrate to 3.4.2S or later. Vulnerable; migrate to 3.4.2S or later.
2.5.x Vulnerable; migrate to 3.4.2S or later. Vulnerable; migrate to 3.4.2S or later.
2.6.x Vulnerable; migrate to 3.4.2S or later. Vulnerable; migrate to 3.4.2S or later.
3.1.xS Vulnerable; migrate to 3.4.2S or later. Vulnerable; migrate to 3.4.2S or later.
3.2.xSG Not Vulnerable Vulnerable; migrate to 3.2.2SG or later.
3.2.xS Vulnerable; migrate to 3.4.2S or later. Vulnerable; migrate to 3.4.2S or later.
3.2.xSG Not Vulnerable 3.2.2SG
3.3.xS Vulnerable; migrate to 3.4.2S or later. Vulnerable; migrate to 3.4.2S or later.
3.3.xSG Not Vulnerable Not Vulnerable
3.4.xS 3.4.2S 3.4.2S
3.5.xS Not vulnerable   3.5.1S
3.6.xS Not vulnerable Not vulnerable

For a mapping of Cisco IOS XE Software releases to Cisco IOS Software releases, refer to Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S Release Notes, and Cisco IOS XE 3SG Release Notes.

Cisco IOS XR Software

Cisco IOS XR Software is not affected by any of the vulnerabilities disclosed in the March 2012 Cisco IOS Software Security Advisory Bundled Publication.


Workarounds

If disabling the IOS SSH Server is not feasible, the following workarounds may be useful to some customers in their environments.

SSH version 1

This vulnerability only affects SSHv2, so it can be temporarily mitigated by applying the ip ssh version 1 global configuration command until a software update can be completed.  Customers should be aware of the limitations and vulnerabilities of SSH version 1 protocol before applying this workaround.

vty Access Class

It is possible to limit the exposure of the Cisco device by applying a vty access class to allow only known, trusted hosts to connect to the device via SSH.

For more information on restricting traffic to a vty, please consult: http://www.cisco.com/en/US/docs/ios/12_2/ipaddr/command/reference/1rfip1.html#wp1017389.

The following example permits access to the vty lines from the 192.168.1.0/24 netblock and the single IP address 172.16.1.2 while denying access from anywhere else:

Router(config)# access-list 1 permit 192.168.1.0 0.0.0.255
Router(config)# access-list 1 permit host 172.16.1.2
Router(config)# line vty 0 4
Router(config-line)# access-class 1 in

Different Cisco platforms support a different amount of terminal lines. Check your device's configuration to determine the correct number of terminal lines for your platform.

Infrastructure Access Control Lists

Although it is often difficult to block traffic transiting your network, it is possible to identify traffic that should never be allowed to target your infrastructure devices and block that traffic at the border of your network. Infrastructure access control lists (iACLs) are considered a network security best practice and should be considered as a long-term addition to good network security as well as a workaround for this specific vulnerability. The ACL example shown below should be included as part of the deployed infrastructure access-list, which will protect all devices with IP addresses in the infrastructure IP address range.

A sample access list for devices running Cisco IOS is below:

!--- Permit SSH services from trusted hosts destined 

!--- to infrastructure addresses.

access-list 150 permit tcp TRUSTED_HOSTS MASK INFRASTRUCTURE_ADDRESSES MASK eq 22

!--- Deny SSH packets from all other sources destined to infrastructure addresses.

access-list 150 deny   tcp any INFRASTRUCTURE_ADDRESSES MASK eq 22

!--- Permit all other traffic to transit the device.

access-list 150 permit IP any any

interface serial 2/0

  ip access-group 150 in

The white paper titled "Protecting Your Core: Infrastructure Protection Access Control Lists" presents guidelines and recommended deployment techniques for infrastructure protection access lists. This white paper is located at http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801a1a55.shtml.

Control Plane Policing

The Control Plane Policing (CoPP) feature may be used to mitigate these vulnerabilities. In the following example, only SSH traffic from trusted hosts with receive destination IP addresses is permitted to reach the route processor (RP).

Note: Dropping traffic from unknown or untrusted IP addresses may affect hosts with dynamically assigned IP addresses from connecting to the Cisco IOS device.

    access-list 152 deny   tcp TRUSTED_ADDRESSES MASK any eq 22

    access-list 152 permit tcp any any eq 22

    !

    class-map match-all COPP-KNOWN-UNDESIRABLE

     match access-group 152

    !

    !

    policy-map COPP-INPUT-POLICY

     class COPP-KNOWN-UNDESIRABLE

      drop

    !

    control-plane

     service-policy input COPP-INPUT-POLICY

In the above CoPP example, the ACL entries that match the exploit packets with the permit action result in these packets being discarded by the policy-map drop function, while packets that match the deny action are not affected by the policy-map drop function.

Additional information on the configuration and use of the CoPP feature can be found at the following URL: http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6586/ps6642/prod_white_paper0900aecd804fa16a.html

Obtaining Fixed Software

Cisco has released free software updates that address the vulnerability described in this advisory. Prior to deploying software, customers are advised to consult their maintenance providers or check the software for feature set compatibility and known issues that are specific to their environments.

Customers may only install and expect support for feature sets they have purchased. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license at http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html, or as set forth at http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

Do not contact psirt@cisco.com or security-alert@cisco.com for software upgrades.

Customers with Service Contracts

Customers with contracts should obtain upgraded software through their regular update channels. For most customers, upgrades should be obtained through the Software Center on Cisco.com at http://www.cisco.com.

Customers Using Third-Party Support Organizations

Customers with Cisco products that are provided or maintained through prior or existing agreements with third-party support organizations, such as Cisco Partners, authorized resellers, or service providers, should contact that organization for assistance with the appropriate course of action.

The effectiveness of any workaround or fix depends on specific customer situations, such as product mix, network topology, traffic behavior, and organizational mission. Because of the variety of affected products and releases, customers should consult their service providers or support organizations to ensure that any applied workaround or fix is the most appropriate in the intended network before it is deployed.

Customers Without Service Contracts

Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco Technical Assistance Center (TAC):

  • +1 800 553 2447 (toll free from within North America)
  • +1 408 526 7209 (toll call from anywhere in the world)
  • e-mail: tac@cisco.com

Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade. Customers without service contracts should request free upgrades through the TAC.

Refer to Cisco Worldwide Contacts at http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html for additional TAC contact information, including localized telephone numbers, instructions, and e-mail addresses for support in various languages.

Exploitation and Public Announcements

The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

This vulnerability was reported to Cisco by a customer.

Status of This Notice: Final

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.

A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.


Distribution

This advisory is posted on Cisco Security Intelligence Operations at the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120328-ssh

Additionally, a text version of this advisory is clear signed with the Cisco PSIRT PGP key and circulated among the following e-mail addresses:

  • cust-security-announce@cisco.com
  • first-bulletins@lists.first.org
  • bugtraq@securityfocus.com
  • vulnwatch@vulnwatch.org
  • cisco@spot.colorado.edu
  • cisco-nsp@puck.nether.net
  • full-disclosure@lists.grok.org.uk

Future updates of this advisory, if any, will reside on Cisco.com but may not be announced on mailing lists. Users can monitor this advisory's URL for any updates.


Revision History

Revision 1.0 2012-March-28 Initial public release

Cisco Security Procedures

Complete information about reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco is available on Cisco.com at http://www.cisco.com/web/about/security/psirt/security_vulnerability_policy.html. This web page includes instructions for press inquiries regarding Cisco Security Advisories. All Cisco Security Advisories are available at http://www.cisco.com/go/psirt.


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