Cisco Security Advisory

Cisco Service Control Engine Denial of Service Vulnerabilities

Advisory ID: cisco-sa-20080521-sce

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080521-sce

Revision 1.0

For Public Release 2008 May 21 16:00  UTC (GMT)


Summary

Three Secure Shell (SSH) vulnerabilities exist in the Cisco Service Control Engine (SCE) that may result in system instability or a reload of the SCE. The first vulnerability may be triggered during SSH login activity that is conducted within aggressive time frames. The second vulnerability may be triggered with normal SSH login activity in combination with other SCE management actions occurring simultaneously. The third vulnerability may be triggered during SSH login and is specific to the usage of unique invalid authentication credentials.

Cisco has made free upgrade software available to address these vulnerabilities for affected customers. There are no workarounds for these vulnerabilities.

Note: These vulnerabilities are independent of each other; a device may be affected by one vulnerability and not by the others.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080521-sce.

Affected Products

Vulnerable Products

The SCE 1000 and 2000 series devices are affected by the following vulnerabilities if the SSH server on the SCE is enabled:

  • System vulnerability to SSH login activity - affects SCE software versions prior to 3.1.6.
  • SSH login activity leads to illegal Input/Output operations - affects SCE software versions prior to 3.0.7 and 3.1.0.
  • SCE SSH authentication sequence anomaly - affects SCE software versions prior to 3.1.6.

Note: The SCE SSH server is disabled by default.

To determine whether you are running a vulnerable version of Cisco Service Control Operating System (SCOS) software, issue the "Show Version" command-line interface (CLI) command. The following example shows a Cisco SCE that runs software release 3.1.6:

SCE2000#>show version
System version: Version 3.1.6 Build 157
Build time: Mar 31 2008, 18:58:49 (Change-list 303626)
Software version is: Version 3.1.6 Build 157

Products Confirmed Not Vulnerable

No other Cisco products are currently known to be affected by these vulnerabilities.

Details

Cisco SCE 1000 and 2000 series devices provide high-capacity advanced application-level bandwidth optimization, stateful application inspection, session-based classification and control of network traffic. The SCE solution allows for the detection and control of network applications including: web browsing, multimedia streaming, and peer-to-peer (P2P).

This Security Advisory describes multiple distinct vulnerabilities. These vulnerabilities are independent of each other.

  • System vulnerability to SSH login activity

A vulnerability impacting the SCE SSH server may be triggered during SSH login activity, resulting in system instability or a reload of the SCE. Specific SSH processes may encounter temporary resource unavailability if called within aggressive intervals.

This vulnerability is documented in Cisco Bug ID CSCsi68582 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2008-0534.

  • SSH login activity leads to illegal Input/Output operations

A second vulnerability exists in the SCE SSH server that may be triggered with normal SSH traffic to the SCE management interface occurring in conjunction with other management tasks. During this event, an illegal IO operation may impact the SCE management agent, requiring a reboot of the SCE to recover management access.

This vulnerability is documented in Cisco Bug ID CSCsh49563 ( registered customers only) and has been assigned CVE ID CVE-2008-0536.

  • SCE SSH authentication sequence anomaly

A third vulnerability exists in the SCE SSH server that may also be triggered during the SSH login process but unrelated to login attempt frequency or other concurrent management tasks. This issue is triggered by the usage of specific SSH credentials that attempt to change the authentication method, resulting in an authentication sequence anomaly impacting system stability.

This vulnerability is documented in Cisco Bug ID CSCsm14239 ( registered customers only) and has been assigned CVE ID CVE-2008-0535.

Vulnerability Scoring Details

Cisco has provided 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 2.0.

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

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

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.

CSCsi68582 - System vulnerability to SSH login activity ( registered customers only)

Calculate the environmental score of CSCsi68582

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

CSCsh49563 - SSH login activity leads to illegal I/O operations ( registered customers only)

Calculate the environmental score of CSCsh49563

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

CSCsm14239 - SCE SSH authentication sequence anomaly ( registered customers only)

Calculate the environmental score of CSCsm14239

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 these vulnerabilities may result in the loss of management access or, in some cases, cause vulnerable SCE devices to reload.

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.

The following list contains the first fixed software release for each vulnerability:

Vulnerability

Affected Major Release

First Fixed Release

System vulnerability to SSH login activity

1.x

3.1.6

2.x

3.1.6

3.x

3.1.6

SSH login activity leads to illegal IO operations

1.x

3.0.7

2.x

3.0.7

3.x

3.0.7, 3.1.0

SCE SSH authentication sequence anomaly

1.x

3.1.6

2.x

3.1.6

3.x

3.1.6

SCOS software version 3.1.6 contains the fixes for all vulnerabilities described in this document.

SCOS software is available for download from the following location on cisco.com:


Workarounds

There are no workarounds for these vulnerabilities.

Filtering SSH traffic with Access Control Lists (ACLs) to affected SCE devices on the SCE management interface or on screening devices can provide a mitigation technique for these vulnerabilities. Restricting SCE SSH management interface access to only trusted devices through the use of SCE ACLs or Transit ACLs is strongly recommended.

Additional information about SCE ACLs is available in the "Configuring the Management Interface and Security" section of the SCE Software Configuration Guide: http://www.cisco.com/en/US/products/ps6134/products_configuration_guide_chapter09186a00808498b9.html#wp1060396

Additional information about tACLs is available in Transit Access Control Lists: Filtering at Your Edge: http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801afc76.shtml

Obtaining Fixed Software

Cisco has released free software updates that address these vulnerabilities. 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/en/US/docs/general/warranty/English/EU1KEN_.html, or as otherwise set forth at Cisco.com Downloads 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, 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 agreements 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 do not hold a Cisco service contract, and customers who purchase through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should acquire 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

Customers should have their product serial number available and be prepared to give the URL of this notice as evidence of 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 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 vulnerabilities described in this advisory.

The SSH login activity vulnerability was discovered during the resolution of customer support cases.

The illegal Input/Output operation and authentication sequence anomaly were discovered by Cisco during internal testing.

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-20080521-sce

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

2008-May-21

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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