Cisco Security Advisory: Cisco Intrusion Prevention System Management Interface Denial of Service and Fragmented Packet Evasion Vulnerabilities

2006-09-20T00:00:00
ID SECURITYVULNS:DOC:14367
Type securityvulns
Reporter Securityvulns
Modified 2006-09-20T00:00:00

Description

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Cisco Security Advisory: Cisco Intrusion Prevention System Management Interface Denial of Service and Fragmented Packet Evasion Vulnerabilities

Document ID: 71558

Advisory ID: cisco-sa-20060920-ips

http://www.cisco.com/warp/public/707/cisco-sa-20060920-ips.shtml

Revision 1.0

For Public Release 2006 September 20 1600 UTC (GMT)


Contents

Summary
Affected Products
Details
Impact
Software Version and Fixes
Workarounds
Obtaining Fixed Software
Exploitation and Public Announcements
Status of this Notice: FINAL
Distribution
Revision History
Cisco Security Procedures

Summary

Cisco Intrusion Prevention System (IPS) software contains a denial of service vulnerability in web administration interface involving malformed Secure Socket Layer (SSL) packets and a fragmented packet evasion vulnerability.

There is a workaround for the web administration interface SSL denial of service vulnerability. There is no workaround for the fragmented packet IPS evasion vulnerability.

Cisco has made free software available to address these vulnerabilities for affected customers.

This advisory is posted at http://www.cisco.com/warp/public/707/cisco-sa-20060920-ips.shtml.

Affected Products

Vulnerable Products +------------------

The following Cisco IPS/IDS versions are vulnerable to the web administration interface SSL denial of service issue:

  • Cisco IDS 4.1(x) software prior to 4.1(5c)
  • Cisco IPS 5.0(x) software prior to 5.0(6p1)
  • Cisco IPS 5.1(x) software prior to 5.1(2)

The following Cisco IPS versions are vulnerable to the fragmented packet IPS evasion issue:

  • Cisco IPS 5.0(x) software prior to 5.0(6p2)
  • Cisco IPS 5.1(x) software prior to 5.1(2)

All platforms running vulnerable versions of Cisco IPS/IDS software are affected. This includes 4200 series appliances, IDSM2, NM-CIDS router modules, and ASA IPS modules (also referred to as Advanced Inspection and Prevention (AIP) Security Services Module [SSM]).

To determine the version of software running on an IPS/IDS device, log in to the IPS/IDS device via SSH or the console and issue the command show version.

sensor#show version
Application Partition: Cisco Intrusion
Prevention System, Version 5.1(2)S242.0

Products Confirmed Not Vulnerable +--------------------------------

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

Cisco IOS software images including the IPS feature set are not vulnerable to the IPS evasion vulnerability if Virtual Fragment Reassembly (VFR) is enabled. If VFR is not enabled, fragmented IP traffic is not inspected by the IPS component which may allow malicious traffic to evade detection. Please consult the IOS IPS documentation for more information.

http://www.cisco.com/en/US/products/ps6634/products_white_paper0900aecd8043bc32.shtml

Details

Cisco Intrusion Prevention and Detection Systems are a family of network security devices that provide network-based threat prevention services.

The web administration interface of Cisco IPS/IDS devices contains a denial of service vulnerability. It is possible to send a malformed SSLv2 Client Hello packet to the IPS/IDS web administration interface, which may cause the process (mainApp) responsible for managing remote access to fail. This results in an IPS/IDS device becoming unresponsive to all future remote management requests through the web administration interface or the command-line interface (CLI) via SSH and the console. This vulnerability is documented in Cisco bug IDs CSCsd91720 and CSCsd92033. This vulnerability was originally fixed in Cisco IPS version 5.1(2).

By using a specially crafted sequence of fragmented IP packets, it is possible for malicious traffic to evade inspection by a Cisco IPS device. This may allow an attacker to circumvent the protection provided by an IPS device and access internal systems. IPS devices running in inline and promiscuous modes are affected. This vulnerability is documented in Cisco bug IDs CSCse17206 and CSCsf12379. This vulnerability was originally fixed in Cisco IPS version 5.1(2).

Impact

Successful exploitation of the web administration interface SSL denial of service vulnerability may result in the failure of the mainApp process. If the mainApp process fails, the following tasks will cease operation:

  • Reporting alerts to remote monitoring systems
  • Automated modification of access control lists (ACLs) on remote firewall systems (PIX and IOS)
  • Sending SNMP traps

Even though the mainApp has failed, the IPS/IDS device will continue to perform inspection of traffic for malicious activity. If configured, the device will continue to drop packets/connections inline and send TCP resets in response to any malicious activity. IPS/IDS devices must be rebooted to recover from this vulnerability. If an IPS/IDS device is configured with a service account, it is possible to log in to an affected device with the service account via SSH or the console and manually reboot the device.

Successful exploitation of the fragmented packet IPS evasion vulnerability may result in an attacker being able to evade detection by an IPS device. This could allow protected systems to be covertly attacked.

Software Version 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.

+--------------------------------------------+ | Affected Software | Fixed Software | | Version | Version | |----------------------+---------------------| | Cisco IDS 4.1(5b) | Cisco IDS 4.1(5c) | | and earlier | | |----------------------+---------------------| | Cisco IPS 5.0(6p1) | Cisco IPS 5.0(6p2) | | and earlier | | |----------------------+---------------------| | Cisco IPS 5.1(1) and | Cisco IPS 5.1(2) | | earlier | | +--------------------------------------------+

Note: IPS version 5.1(2) is no longer available for download. It has been replaced by IPS version 5.1(3).

Note: Bug ID CSCsd91720 is fixed in IPS version 5.0(6p1), and CSCsf12379 is fixed in IPS version 5.0(6p2).

Fixed software for Cisco IPS versions 5.1(x) are available for download at http://www.cisco.com/pcgi-bin/tablebuild.pl/ips5?psrtdcat20e2

Fixed software for Cisco IPS versions 4.1(x) and 5.0(x) is available for download at http://www.cisco.com/pcgi-bin/tablebuild.pl/ids-patches?psrtdcat20e2

Workarounds

It is possible to limit exposure to the web administration interface SSL denial of service vulnerability by applying an access control list (ACL) on an IPS/IDS device to restrict access to trusted management systems. Instructions to add an ACL can be found at:

http://www.cisco.com/en/US/products/hw/vpndevc/ps4077/products_configuration_guide_chapter09186a008055df9a.html#wp1031536

There is no workaround for the fragmented packet IPS evasion 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.

The web administration interface SSL denial of service vulnerability was discovered internally by Cisco.

The fragmented packet IPS evasion vulnerability was reported to Cisco by Pratap Ramamurthy and Shai Rubin of the Wisconsin Safety Analyzer group (WiSA) in the Computer Science department at the University of Wisconsin.

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://www.cisco.com/warp/public/707/cisco-sa-20060920-ips.shtml

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 | | Initial | | 1.0 | 2006-August-20 | 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/en/US/products/products_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.


All contents are Copyright 1992-2006 Cisco Systems, Inc. All rights reserved.


Updated: Sep 20, 2006 Document ID: 71558


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