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Cisco Security Advisory

Cisco IOS Secure Copy Authorization Bypass Vulnerability

Advisory ID: cisco-sa-20070808-scp

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20070808-scp

Revision 1.1

For Public Release 2007 August 8 16:00  UTC (GMT)

Related Resources:

View related Alert

Summary

The server side of the Secure Copy (SCP) implementation in Cisco Internetwork Operating System (IOS) contains a vulnerability that allows any valid user, regardless of privilege level, to transfer files to and from an IOS device that is configured to be a Secure Copy server. This vulnerability could allow valid users to retrieve or write to any file on the device's filesystem, including the device's saved configuration. This configuration file may include passwords or other sensitive information.

The IOS Secure Copy Server is an optional service that is disabled by default. Devices that are not specifically configured to enable the IOS Secure Copy Server service are not affected by this vulnerability.

This vulnerability does not apply to the IOS Secure Copy Client feature.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20070808-scp.

Note: The August 08, 2007 publication includes four Security Advisories and one Security Response. The advisories all affect IOS, one additionally affects Cisco Unified Communications Manager as well. Each advisory lists the releases that correct the vulnerability described in the advisory, and the advisories also detail the releases that correct the vulnerabilities in all four advisories. Individual publication links are listed below:

Affected Products

Vulnerable Products

Cisco devices running certain 12.2-based IOS releases and configured to offer Secure Copy server functionality are affected by this issue.

A device running a vulnerable Cisco IOS 12.2-based is affected if the following command is present in the device configuration:

ip scp server enable

The IOS Secure Copy server is disabled by default.

The Secure Copy server functionality is only available on encryption-capable images. Devices that do not run an encryption-capable images, which contain either k8 or k9 in the image name, are not vulnerable. If a device is running an encryption-capable image, the existence of the ip scp server enable command in the configuration will determine whether the device is affected.

Please consult the table of fixed software in the Software Version and Fixes section for the specific 12.2-based IOS releases that are affected.

To determine the software running on a Cisco product, log in to the device and issue the show version command to display the system banner. Cisco IOS software will identify itself as "Internetwork Operating System Software" or simply "IOS". The image name will be displayed between parentheses on the next line of output followed by "Version" and IOS release name. Other Cisco devices will not have the show version command or will give different output.

The following example identifies a Cisco product running IOS release 12.2(18)SXF10:

Cisco Internetwork Operating System Software
IOS (tm) s72033_rp Software (s72033_rp-IPSERVICESK9-M), Version 12.2(18)SXF10, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by cisco Systems, Inc.
Compiled Fri 13-Jul-07 08:32 by kellythw

Additional information about Cisco IOS release naming is available at http://www.cisco.com/warp/public/620/1.html.

Products Confirmed Not Vulnerable

Cisco devices that do not run IOS are not affected.

Cisco IOS devices that do not have the Secure Copy server feature enabled are not affected.

The following IOS release trains are not affected:

  • 12.0-based releases
  • 12.1-based releases
  • 12.3-based releases
  • 12.4-based releases

Cisco IOS XR is not affected.

No other Cisco devices are known to be affected.

Details

Secure Copy (SCP) is a protocol similar to the Remote Copy (RCP) protocol, which allows for the transfer of files between systems. The main difference between SCP and RCP is that in SCP, all aspects of the file transfer session, including authentication, occur in encrypted form, which makes SCP a more secure alternative than RCP. SCP relies on the Secure Shell (SSH) protocol, which uses TCP port 22 by default.

The server side of the Secure Copy implementation in Cisco IOS contains a vulnerability that allows any valid user, regardless of privilege level, to transfer files to and from an IOS device that is configured to be a Secure Copy server. This vulnerability could allow valid users to retrieve or write to any file on the device's filesystem, including the device's saved configuration. This configuration file may include passwords or other sensitive information.

This vulnerability does not allow for authentication bypass; login credentials are verified and access is only granted if a valid username and password is provided. This vulnerability may cause authorization to be bypassed.

A device with the Secure Copy server enabled is vulnerable regardless of whether Authentication, Authorization, and Accounting (AAA) is enabled. If access control is enabled on the Virtual Terminal (vty) via the login command, which allows logins via Virtual Terminals, then the device is affected.

This vulnerability is documented in Cisco Bug ID CSCsc19259 ( registered customers only) .

Vulnerability Scoring Details

Cisco is providing scores for the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this Security Advisory is done in accordance with CVSS version 1.0.

Cisco will provide a base and temporal score. Customers can then compute environmental scores to assist in determining the impact of the vulnerability in individual networks.

Cisco PSIRT will set the bias in all cases to normal. Customers are encouraged to apply the bias parameter when determining the environmental impact of a particular vulnerability.

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

Cisco has provided an FAQ to answer additional questions regarding CVSS at

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

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

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

CSCsc19259

Calculate the environmental score of CSCsc19259

CVSS Base Score - 6.0

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Impact Bias

Remote

Low

Required

Complete

Complete

Complete

Normal

CVSS Temporal Score - 5.0

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

Impact

Successful exploitation of the vulnerability described in this advisory may allow valid but unauthorized users to retrieve or write to any file on the device's filesystem, including the device's saved configuration. This configuration file may include passwords or other sensitive information.

Software Versions and Fixes

When considering software upgrades, also consult http://www.cisco.com/go/psirt and any subsequent advisories to determine exposure and a complete upgrade solution.

In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, contact the Cisco Technical Assistance Center ("TAC") or your contracted maintenance provider for assistance.

Each row of the Cisco IOS software table (below) names a Cisco IOS release train. If a given release train is vulnerable, then the earliest possible releases that contain the fix (along with the anticipated date of availability for each, if applicable) are listed in the "First Fixed Release" column of the table. The "Recommended Release" column indicates the releases which have fixes for all the published vulnerabilities at the time of this Advisory. A device running a release in the given train that is earlier than the release in a specific column (less than the First Fixed Release) is known to be vulnerable. Cisco recommends upgrading to a release equal to or later than the release in the "Recommended Releases" column of the table.

For further information about how Cisco IOS is built, numbered and maintained, please see the following URL: http://www.cisco.com/warp/public/620/1.html

Major Release

Availability of Repaired Releases

Affected 12.0-Based Release

First Fixed Release

Recommended Release

There are no affected 12.0 based releases

Affected 12.1-Based Release

First Fixed Release

Recommended Release

There are no affected 12.1 based releases

Affected 12.2-Based Release

First Fixed Release

Recommended Release

12.2

Not Vulnerable

 

12.2B

Not Vulnerable

 

12.2BC

Not Vulnerable

 

12.2BW

Not Vulnerable

 

12.2BY

Not Vulnerable

 

12.2BZ

Not Vulnerable

 

12.2CX

Not Vulnerable

 

12.2CY

Not Vulnerable

 

12.2CZ

Not Vulnerable

 

12.2DA

Not Vulnerable

 

12.2DD

Not Vulnerable

 

12.2DX

Not Vulnerable

 

12.2EU

Not Vulnerable

 

12.2EW

Not Vulnerable

 

12.2EWA

Not Vulnerable

 

12.2EX

Not Vulnerable

 

12.2EY

Not Vulnerable

 

12.2EZ

Not Vulnerable

 

12.2FX

Not Vulnerable

 

12.2FY

Not Vulnerable

 

12.2FZ

Not Vulnerable

 

12.2IXA

Vulnerable; first fixed in 12.2(18)IXD1

12.2(18)IXD1

12.2IXB

Vulnerable; first fixed in 12.2(18)IXD1

12.2(18)IXD1

12.2IXC

Vulnerable; first fixed in 12.2(18)IXD1

12.2(18)IXD1

12.2IXD

12.2(18)IXD1

12.2(18)IXD1

12.2JA

Not Vulnerable

 

12.2JK

Not Vulnerable

 

12.2MB

Not Vulnerable

 

12.2MC

Not Vulnerable

 

12.2S

Not Vulnerable

 

12.2SB

Not Vulnerable

 

12.2SBC

Not Vulnerable

 

12.2SE

Not Vulnerable

 

12.2SEA

Not Vulnerable

 

12.2SEB

Not Vulnerable

 

12.2SEC

Not Vulnerable

 

12.2SED

Not Vulnerable

 

12.2SEE

Not Vulnerable

 

12.2SEF

Not Vulnerable

 

12.2SEG

Not Vulnerable

 

12.2SG

Not Vulnerable

 

12.2SGA

Not Vulnerable

 

12.2SL

Not Vulnerable

 

12.2SM

Not Vulnerable

 

12.2SO

Not Vulnerable

 

12.2SRA

Not Vulnerable

 

12.2SRB

Not Vulnerable

 

12.2SU

Not Vulnerable

 

12.2SV

Not Vulnerable

 

12.2SVA

Not Vulnerable

 

12.2SVC

Not Vulnerable

 

12.2SW

Not Vulnerable

 

12.2SX

Not Vulnerable

 

12.2SXA

Not Vulnerable

 

12.2SXB

Not Vulnerable

 

12.2SXD

Vulnerable; contact TAC

 

12.2SXE

Vulnerable; first fixed in 12.2(18)SXF9

12.2(18)SXF10

12.2SXF

12.2(18)SXF9

12.2(18)SXF10

12.2SXH

Not Vulnerable

 

12.2SY

Not Vulnerable

 

12.2SZ

Not Vulnerable

 

12.2T

Not Vulnerable

 

12.2TPC

Not Vulnerable

 

12.2UZ

Not Vulnerable

 

12.2VZ

Not Vulnerable

 

12.2XA

Not Vulnerable

 

12.2XB

Not Vulnerable

 

12.2XC

Not Vulnerable

 

12.2XD

Not Vulnerable

 

12.2XE

Not Vulnerable

 

12.2XF

Not Vulnerable

 

12.2XG

Not Vulnerable

 

12.2XH

Not Vulnerable

 

12.2XI

Not Vulnerable

 

12.2XJ

Not Vulnerable

 

12.2XK

Not Vulnerable

 

12.2XL

Not Vulnerable

 

12.2XM

Not Vulnerable

 

12.2XN

Not Vulnerable

 

12.2XQ

Not Vulnerable

 

12.2XR

Not Vulnerable

 

12.2XS

Not Vulnerable

 

12.2XT

Not Vulnerable

 

12.2XU

Not Vulnerable

 

12.2XV

Not Vulnerable

 

12.2XW

Not Vulnerable

 

12.2YA

Not Vulnerable

 

12.2YB

Not Vulnerable

 

12.2YC

Not Vulnerable

 

12.2YD

Not Vulnerable

 

12.2YE

Not Vulnerable

 

12.2YF

Not Vulnerable

 

12.2YG

Not Vulnerable

 

12.2YH

Not Vulnerable

 

12.2YJ

Not Vulnerable

 

12.2YK

Not Vulnerable

 

12.2YL

Not Vulnerable

 

12.2YM

Not Vulnerable

 

12.2YN

Not Vulnerable

 

12.2YO

Not Vulnerable

 

12.2YP

Not Vulnerable

 

12.2YQ

Not Vulnerable

 

12.2YR

Not Vulnerable

 

12.2YS

Not Vulnerable

 

12.2YT

Not Vulnerable

 

12.2YU

Not Vulnerable

 

12.2YV

Not Vulnerable

 

12.2YW

Not Vulnerable

 

12.2YX

Not Vulnerable

 

12.2YY

Not Vulnerable

 

12.2YZ

Not Vulnerable

 

12.2ZA

Not Vulnerable

 

12.2ZB

Not Vulnerable

 

12.2ZC

Not Vulnerable

 

12.2ZD

Not Vulnerable

 

12.2ZE

Not Vulnerable

 

12.2ZF

Not Vulnerable

 

12.2ZG

Not Vulnerable

 

12.2ZH

Not Vulnerable

 

12.2ZJ

Not Vulnerable

 

12.2ZL

Not Vulnerable

 

12.2ZP

Not Vulnerable

 

12.2ZR

Not Vulnerable

 

12.2ZU

Vulnerable; first fixed in 12.2(33)SXH available 31-Aug-07

12.2(33)SXH; available 31-Aug-07

12.2ZW

Not Vulnerable

 

12.2ZY

Not Vulnerable

 

Affected 12.3-Based Release

First Fixed Release

Recommended Release

There are no affected 12.3 based releases

Affected 12.4-Based Release

First Fixed Release

Recommended Release

There are no affected 12.4 based releases


Workarounds

If the IOS Secure Copy Server functionality is not needed then the vulnerability described in this document can be mitigated by disabling the Secure Copy server. The Secure Copy server can be disabled by executing the following command in global configuration mode:

no ip scp server enable

If the Secure Copy server cannot be disabled due to operational concerns, then no workarounds exist. The risk posed by this vulnerability can be mitigated by following the best practices detailed in "Improving Security on Cisco Routers" at http://www.cisco.com/warp/public/707/21.html. Please refer to the Obtaining Fixed Software section for appropriate solutions to resolve this vulnerability.

Due to the nature of this vulnerability, networking best practices like access control lists (ACLs) and Control Plane Policing (CoPP) that restrict access to a device to certain IP addresses or subnetworks may not be effective. If access is already granted to a specific IP address or subnetwork, a user with low privileges will be able to establish a Secure Copy session with the device, which would allow the user to exploit this vulnerability.

Obtaining Fixed Software

Cisco will make free software available to address this vulnerability for affected customers. This advisory will be updated as fixed software becomes available. Prior to deploying software, customers should consult their maintenance provider or check the software for feature set compatibility and known issues specific to their environment.

Customers may only install and expect support for the feature sets they have purchased. By installing, downloading, accessing or otherwise using such software upgrades, customers agree to be bound by the terms of Cisco's software license terms found at http://www.cisco.com/public/sw-license-agreement.html, or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

Do not contact either "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, this means that upgrades should be obtained through the Software Center on Cisco's worldwide website at http://www.cisco.com.

Customers Using Third-Party Support Organizations

Customers whose Cisco products are provided or maintained through prior or existing agreement with third-party support organizations such as Cisco Partners, authorized resellers, or service providers should contact that support organization for guidance and assistance with the appropriate course of action in regards to this advisory.

The effectiveness of any workaround or fix is dependent on specific customer situations such as product mix, network topology, traffic behavior, and organizational mission. Due to the variety of affected products and releases, customers should consult with their service provider or support organization to ensure any applied workaround or fix is the most appropriate for use in the intended network before it is deployed.

Customers Without Service Contracts

Customers who purchase direct from Cisco but who do not hold a Cisco service contract and customers who purchase through third-party vendors but are unsuccessful at obtaining fixed software through their point of sale should get their upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC contacts are as follows.

  • +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

Have your product serial number available and give the URL of this notice as evidence of your entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC.

Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for additional TAC contact information, including special localized telephone numbers and instructions and e-mail addresses for use in various languages.

Exploitation and Public Announcements

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.

This vulnerability was reported to Cisco by Vijay Sarvepalli from University of North Carolina at Greensboro.

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's worldwide website at:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20070808-scp

In addition to worldwide web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail and Usenet news recipients.

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

Future updates of this advisory, if any, will be placed on Cisco's worldwide website, but may or may not be actively announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check the above URL for any updates.


Revision History

Revision 1.0

2007-August-08

Initial public release

Cisco Security Procedures

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


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