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Cisco Security Advisory

Cisco IronPort Appliances Telnet Remote Code Execution Vulnerability

Advisory ID: cisco-sa-20120126-ironport

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120126-ironport

Revision 2.0

Last Updated  2014 October 16 13:40  UTC (GMT)

For Public Release 2012 January 26 17:00  UTC (GMT)

Related Resources:

View related IPS SignatureView related Applied Mitigation Bulletin

Summary

Cisco AsyncOS Software for Cisco Web Security Appliance (WSA), Cisco Email Security Appliance (ESA), and Cisco Content Security Management Appliance (SMA) contain a vulnerability that may allow a remote, unauthenticated attacker to execute arbitrary code with elevated privileges.

Cisco has released free software updates that address this vulnerability. Workarounds that mitigate this vulnerability are available.

Note: This security advisory has been updated to include important information about Cisco WSA

This advisory is available at the following link:
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120126-ironport

Affected Products

Vulnerable Products

The following products running an affected version of Cisco AsyncOS Software are affected:
  • All models of Cisco ESA hardware appliances
  • All models of Cisco SMA hardware appliances
  • All models of Cisco WSA both hardware and virtual appliances

Note: The Cisco AsyncOS Software for Cisco WSA is affected by this vulnerability only if the System Setup Wizard (SSW) has not been performed as the Telnet access is disabled after the setup is completed.
Cisco WSA will not fully operate unless the SSW has completed; this limits the scope of the vulnerability on Cisco WSA.

This vulnerability can only be exploited if Telnet is enabled on the affected system for remote access. To determine whether the system has Telnet enabled, administrators can use the netstat command and verify that the default Telnet TCP port 23 is in listening state. The following example shows a Cisco ESA with telnet enabled:

ciscoesa> netstat

Active Internet connections (including servers)
Proto Recv-Q Send-Q  Local Address          Foreign Address       (state)
[...]
tcp4       0      0 172.18.254.80.21       *.*                    LISTEN
tcp4       0      0 172.18.254.80.22       *.*                    LISTEN
tcp4       0      0 172.18.254.80.23       *.*                    LISTEN      

[...]

Determining the Running Software Version

To determine whether a vulnerable version of Cisco AsyncOS Software is running on an appliance, administrators can issue the version command. The following example shows a device running Cisco  AsyncOS Software for Cisco ESA Software version 7.6.2-201:

ciscoesa> version
Current Version
===============
Product: Cisco IronPort X1070 Messaging Gateway(tm) Appliance
Model: X1070
Version: 7.6.2-201
[...]

Products Confirmed Not Vulnerable

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

Details

The Cisco ESA provides email management and protection combining antispam, antivirus, encryption, digital rights management, and archiving technologies. The Cisco SMA is a flexible management tool designed to centralize and consolidate policy and runtime data, providing a single management interface for multiple Cisco IronPort security appliances.

The Cisco WSA is a secure web gateway that combines advanced malware protection, application visibility and control (AVC), acceptable use policy controls, reporting, and secure mobility on a single platform.

A vulnerability in telnet code of Cisco AsyncOS could allow an unauthenticated, remote attacker to to execute arbitrary code on the affected system.

The vulnerability is due to insufficient boundary checks when processing telnet encryption keys.  An unauthenticated, remote attacker could exploit this vulnerability by sending malicious requests to a targeted system.  If successful, the attacker could execute arbitrary code on the system with elevated privileges.



Note: The Cisco AsyncOS Software for Cisco WSA is affected by this vulnerability only if the System Setup Wizard (SSW) has not been performed as the Telnet access is disabled after the setup is completed.
Cisco WSA will not fully operate unless the SSW has completed; this limits the scope of the vulnerability on Cisco WSA.

This vulnerability is documented by Cisco bug IDs CSCzv32432 (registered customers only) for Cisco ESA, CSCzv44580 (registered customers only) for Cisco SMA, and CSCuo90523 (registered customers only) for Cisco WSA.

The vulnerability was previously documented in Cisco IronPort bug 83262. Cisco IronPort tracks bugs using an internal system that is not available to customers. The Cisco IronPort bug tracking identifiers are provided for reference only.

This vulnerability has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2011-4862.


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





CSCzv32432 and CSCzv44580 - Cisco AsyncOS BSD telnetd command execution vulnerability (ESA and SMA)

Calculate the environmental score of CSCzv32432 and CSCzv44580

CVSS Base Score - 10.0

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

Complete

Complete

Complete

CVSS Temporal Score - 9.0

Exploitability

Remediation Level

Report Confidence

Functional

Workaround

Confirmed




 CSCuo90523 - Cisco AsyncOS BSD telnetd command execution vulnerability (WSA)

Calculate the environmental score of CSCuo90523

CVSS Base Score - 7.6

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

High

None

Complete

Complete

Complete

CVSS Temporal Score - 6.3

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed


Impact

Successful exploitation of this vulnerability could allow a remote, unauthenticated attacker to execute arbitrary code with elevated privileges.

Software Versions and Fixes

When considering software upgrades, customers are advised to consult the Cisco Security Advisories, Responses, and Notices 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.

The following tables include the first fixed releases for Cisco AsyncOS Software for Cisco ESA:

 Major Release
 First Fixed In
 7.1 and prior
 7.1.5-101
 7.3  7.3.1-101
 7.5  7.5.1-102
 7.6  7.6.1-022
 8.0  Not Affected
 8.5  Not Affected
 8.6  Not Affected


The following tables include the first fixed releases for Cisco AsyncOS Software for Cisco SMA:


 Major Release
 First Fixed In
 7.2 and prior
 7.2.2-106
 7.7  7.7.0-206
 7.8  Not Available - Upgrade to 7.9 or later
 7.9  7.9.1-102
 8.0  Not Affected
 8.1  Not Affected
 8.2  Not Affected
 8.3  Not Affected



The following tables include the first fixed releases for Cisco AsyncOS Software for Cisco WSA:

 Major Release
 First Fixed In
 7.1 and prior
 Not Available - Upgrade to 7.7 or later
 7.5  Not Available - Upgrade to 7.7 or later
 7.7  7.7.0-757
 8.0  8.0.6-073
 8.1  8.1.0-235

Workarounds

For some versions of Cisco AsyncOS Software for Cisco ESA and Cisco SMA, Telnet is configured on the Management port. Telnet services can be disabled to mitigate this vulnerability. Administrators can disable Telnet by using the administration graphical user interface (GUI) or by using the interfaceconfig command in the command-line interface (CLI). As a security best practice, customers should use Secure Shell (SSH) instead of Telnet.

Complete the following steps to disable Telnet via the GUI:

Step 1: Navigate to Network > IP Interfaces > interface_name.
Step 2: Remove the check from the box next to the Telnet service.
Step 3: Click on the Submit button to submit the change.
Step 4: Click the Commit Change button for these changes to take effect.

Use the interfaceconfig command, as shown in the example below to disable Telnet via the CLI.

ciscoesa> interfaceconfig

Currently configured interfaces:
1. Data 1 (192.168.1.1/24 on Data1: mail3.example.com)
2. Data 2 (192.168.2.1/24 on Data2: mail3.example.com)
3. Management (192.168.42.42/24 on Management: mail3.example.com)

Choose the operation you want to perform:
- NEW - Create a new interface.
- EDIT - Modify an interface.
- GROUPS - Define interface groups.
- DELETE - Remove an interface.

[]> edit
Enter the number of the interface you wish to edit.
[]> 3

<..output omitted>

Do you want to enable Telnet on this interface? [N]> N
Do you want to enable SSH on this interface? [N]> Y

Note: The interfaceconfig command is described in detail in the section Other Tasks in the GUI in the Cisco AsyncOS Daily Management Guide available at the following link:
http://www.cisco.com/en/US/docs/security/esa/esa7.5/ESA_7.5_Daily_Management_Guide.pdf

Cisco AsyncOS Software for Cisco WSA has Telnet enabled by default; however once SSW is completed, telnet will be automatically disabled.

The Cisco Applied Mitigation Bulletin (AMB) "Identifying and Mitigating Exploitation of the Cisco IronPort Appliances Telnet Remote Code Execution Vulnerability", is available at http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20120126-ironport

Obtaining Fixed Software

Cisco has released free software updates that address the vulnerabilities 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.

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 vulnerability in the telnetd service that affects Cisco AsyncOS Software for Cisco ESA, Cisco SMA, and Cisco WSA was publicly disclosed by the FreeBSD Project on December 23rd, 2011. The FreeBSD Project advisory is available at:

http://security.freebsd.org/advisories/FreeBSD-SA-11:08.telnetd.asc

The vulnerability on Cisco WSA was reported to Cisco by Glafkos Charalambous

The Cisco Product Security Incident Response Team (PSIRT) is aware of exploit modules for the Metasploit Framework that can exploit this vulnerability on affected Cisco AsyncOS Software versions.

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-20120126-ironport

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 2.0 2014-October-16 Added important information about Cisco WSA.
Revision 1.4 2012-July-14 Updated meta-tags for Affected Products.
Revision 1.3 2012-February-08 Updated advisory to fix minor HTML formatting issue.
Revision 1.2 2012-February-07 Updated advisory to include the availability of IronPort software updates.
Revision 1.1 2012-January-26 Updated advisory to include the availability of a Cisco Applied Mitigation Bulletin.
Revision 1.0 2012-January-26 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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