Cisco Security Advisory

Multiple Vulnerabilities in Cisco Firewall Services Module

Advisory ID: cisco-sa-20111005-fwsm

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20111005-fwsm

Revision 1.1

Last Updated  2012 July 14 10:13  UTC (GMT)

For Public Release 2011 October 5 16:00  UTC (GMT)


Summary

The Cisco Firewall Services Module (FWSM) for the Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers is affected by the following vulnerabilities:

  • Syslog Message Memory Corruption Denial of Service Vulnerability
  • Authentication Proxy Denial of Service Vulnerability
  • TACACS+ Authentication Bypass Vulnerability
  • Sun Remote Procedure Call (SunRPC) Inspection Denial of Service Vulnerabilities
  • Internet Locator Server (ILS) Inspection Denial of Service Vulnerability

These vulnerabilities are not interdependent; a release that is affected by one vulnerability is not necessarily affected by the others.

Cisco has released free software updates that address these vulnerabilities. Workarounds are available for some of the vulnerabilities disclosed in this advisory.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20111005-fwsm.

Note: Cisco ASA 5500 Series Adaptive Security Appliances and the Cisco Catalyst 6500 Series ASA Services Module are affected by some of the vulnerabilities described in this advisory. A separate Cisco Security Advisory has been published to disclose these and other vulnerabilities that affect the Cisco ASA 5500 Series Adaptive Security Appliances and the Cisco Catalyst 6500 Series ASA Services Module. The advisory is available at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20111005-asa.

Affected Products

Vulnerable Products

The Cisco FWSM for the Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers is affected by multiple vulnerabilities. Affected versions of Cisco FWSM Software vary depending on the specific vulnerability. Refer to the "Software Version and Fixes" section for specific information on vulnerable versions.

Syslog Message Memory Corruption Denial of Service Vulnerability

Devices running vulnerable versions of Cisco FWSM Software are affected by this vulnerability if the following conditions are satisfied:

  • The device has interfaces with IPv6 addresses
  • System logging is enabled (command logging enable)
  • The device is configured in any way to generate system log message 302015 (refer to the following examples)

System log message 302015 has a default severity level of 6 (informational) so, assuming that the system administrator has not changed this default severity level, the vulnerability can be triggered if the device is logging to any destination at level 6 or level 7 (debug). As an example, the following configuration is vulnerable:

logging enable
!
logging console informational
logging buffered informational
[...]

Using a custom message list (via the logging list command) that includes system log message 302015, either by severity or by explicitly including the message ID, is also a vulnerable configuration. For example, the following configuration is also vulnerable:

logging enable
!
logging list MYLIST level informational
<and/or>
logging list MYLIST message 302015
!
logging trap MYLIST

Note: The default severity level of system log messages can be changed. If the default severity level of system log message 302015 is changed, and the device is configured to log to any destination at the new severity level, then the device is still vulnerable.

Authentication Proxy Denial of Service Vulnerability

Devices running vulnerable versions of Cisco FWSM Software are affected by this vulnerability if they are configured to use Authentication, Authorization, and Accounting (AAA) for network access, also known as cut-through or authentication proxy. The network access authentication feature is enabled if the aaa authentication match or aaa authentication include commands are present in the configuration of an affected device.

TACACS+ Authentication Bypass Vulnerability

Devices running vulnerable versions of Cisco FWSM Software are affected by this vulnerability if they are configured to use the Terminal Access Controller Access-Control System Plus (TACACS+) protocol for AAA. A device is configured for TACACS+ if an AAA server group is defined in a manner similar to the following:

aaa-server my-tacacs-server protocol tacacs+
aaa-server my-tacacs-server (inside) host 192.168.1.1
  [...]

Note: In the preceding example, "my-tacacs-server" is the name of the AAA server group.

SunRPC Inspection Denial of Service Vulnerabilities

Devices running vulnerable versions of Cisco FWSM Software are affected by these vulnerabilities if SunRPC inspection is enabled. SunRPC inspection is enabled by default.

To determine whether SunRPC inspection is enabled, issue the show service-policy | include sunrpc command and confirm that the command returns output. Example output follows:

FWSM# show service-policy | include sunrpc
      Inspect: sunrpc, packet 324, drop 5, reset-drop 0

Alternatively, a device with SunRPC inspection enabled has a configuration similar to the following (the inspect sunrpc command is the command that actually enables SunRPC inspection, although the other commands are necessary for the Cisco FWSM to actually inspect traffic):

class-map inspection_default
 match default-inspection-traffic
!
policy-map global_policy
 class inspection_default
  ...
  inspect sunrpc 
!
service-policy global_policy global

Note: The service policy could also be applied to a specific interface. (Global application is shown in the previous example.)

ILS Inspection Denial of Service Vulnerability

Devices running vulnerable versions of Cisco FWSM Software are affected by these vulnerabilities if inspection of the ILS protocol is enabled. ILS inspection is not enabled by default.

Refer to "SunRPC Inspection Denial of Service Vulnerabilities" for information on how to determine if ILS inspection is enabled. Use the configuration keyword "ils" instead of "sunrpc".

How to Determine the Running Software Version

To determine the version of Cisco FWSM Software that is running on a device, issue the show module command from Cisco IOS Software or Cisco Catalyst Operating System Software to identify what modules and submodules are installed on the system.

The following example shows a system with a Cisco FWSM (WS-SVC-FWM-1) installed in slot 2:

switch>show module
Mod Ports Card Type                              Model              Serial No.
--- ----- -------------------------------------- ------------------ -----------
  1   16  SFM-capable 16 port 1000mb GBIC        WS-X6516-GBIC      SAL06334NS9
  2    6  Firewall Module                        WS-SVC-FWM-1       SAD10360485
  3    8  Intrusion Detection System             WS-SVC-IDSM-2      SAD0932089Z
  4    4  SLB Application Processor Complex      WS-X6066-SLB-APC   SAD093004BD
  5    2  Supervisor Engine 720 (Active)         WS-SUP720-3B       SAL0934888E

Mod MAC addresses                       Hw    Fw           Sw           Status
--- ---------------------------------- ------ ------------ ------------ -------
  1  0009.11e3.ade8 to 0009.11e3.adf7   5.1   6.3(1)       8.7(0.22)BUB Ok
  2  0018.ba41.5092 to 0018.ba41.5099   4.0   7.2(1)       4.0(16)      Ok
  3  0014.a90c.9956 to 0014.a90c.995d   5.0   7.2(1)       7.0(4)E4     Ok
  4  0014.a90c.66e6 to 0014.a90c.66ed   1.7   Unknown      Unknown      PwrDown
  5  0013.c42e.7fe0 to 0013.c42e.7fe3   4.4   8.1(3)       12.2(33)SXH8 Ok

[...]

After locating the correct slot, issue the show module <slot number> command to identify the software version that is running, as shown in the following example:

switch>show module 2
Mod Ports Card Type                              Model              Serial No.
--- ----- -------------------------------------- ------------------ -----------
  2    6  Firewall Module                        WS-SVC-FWM-1       SAD10360485

Mod MAC addresses                       Hw    Fw           Sw           Status
--- ---------------------------------- ------ ------------ ------------ -------
  2  0018.ba41.5092 to 0018.ba41.5099   4.0   7.2(1)       4.0(16)      Ok

[...]

The preceding example shows that the Cisco FWSM is running software version 4.0(16) as indicated by the Sw column.

Note: Recent versions of Cisco IOS Software will show the software version of each module in the output from the show module command; therefore, executing the show module <slot number> command is not necessary.

If a Virtual Switching System (VSS) is used to allow two physical Cisco Catalyst 6500 Series switches to operate as a single logical virtual switch, the show module switch all command can display the software version of all FWSMs that belong to switch 1 and switch 2. The output from this command will be similar to the output from show module <slot number> but will include module information for the modules in each switch in the VSS.

Alternatively, version information can be obtained directly from the Cisco FWSM through the show version command, as shown in the following example:

FWSM> show version

FWSM Firewall Version 4.0(16)
[...]

Customers who use the Cisco Adaptive Security Device Manager (ASDM) to manage their devices can find the version of the software displayed in the table in the login window or in the upper left corner of the Cisco ASDM window. The version notation is similar to the following example:

FWSM Version: 4.0(16)

Products Confirmed Not Vulnerable

With the exception of Cisco ASA 5500 Series Adaptive Security Appliances and the Cisco Catalyst 6500 Series ASA Services Module, no other Cisco products are currently known to be affected by these vulnerabilities.

Details

The Cisco FWSM is a high-speed, integrated firewall module for Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers. The FWSM offers firewall services with stateful packet filtering and deep packet inspection.

The Cisco FWSM is affected by multiple vulnerabilities, which are described in the following sections.

Syslog Message Memory Corruption Denial of Service Vulnerability

The Cisco FWSM has a system log (syslog) feature that provides information for monitoring normal operation and troubleshooting network or device issues. System log messages are assigned different severities (debugging, informational, error, critical, etc.) and can be sent to different logging destinations.

A denial of service vulnerability exists in the implementation of one specific system log message (message ID 302015, "Built outbound UDP connection session-id for src-intf:IP/Port to dst-intf:IP/Port ARP-Incomplete") that can cause memory corruption and lead to a lock up or crash of the Cisco FWSM in the event that that system log message needs to be generated for IPv6 traffic that has flowed through the device. The Cisco FWSM may not recover on its own and a manual reboot may be necessary to recover.

System log message 302015 has a default severity level of 6 (informational). Changing the default severity level of this system message will not prevent the issue from occurring if the system is logging to any destinations at the new severity level. The Cisco FWSM must have interfaces with IPv6 addresses otherwise the problem does not occur.

This vulnerability is documented in Cisco bug ID CSCti83875 ( registered customers only) and has been assigned CVE ID CVE-2011-3296.

Authentication Proxy Denial of Service Vulnerability

The Cisco FWSM authentication proxy feature allows one to use AAA to control access to network resources. Specifically, the Cisco FWSM cut-through proxy challenges a user initially at the application layer and then authenticates against AAA servers. After the Cisco FWSM authenticates the user, it shifts the session flow, and all traffic flows directly between the user's computer and the network resource being accessed.

A denial of service vulnerability exists in some versions of Cisco FWSM Software that affects devices configured to use authentication to grant users access to the network, also known as cut-through or authentication proxy. Vulnerable configurations are those that contain the aaa authentication match or aaa authentication include commands. The vulnerability may be triggered when there is a high number of network access authentication requests.

This vulnerability is documented in Cisco bug ID CSCtn15697 ( registered customers only) and has been assigned CVE ID CVE-2011-3297.

TACACS+ Authentication Bypass Vulnerability

AAA enables the Cisco FWSM to determine who the user is (authentication), what the user can do (authorization), and what the user did (accounting). The Cisco FWSM supports TACACS+ authentication for VPN users, firewall sessions, and administrative access to the device.

An authentication bypass vulnerability exists in the TACACS+ implementation in the Cisco FWSM. Successful exploitation could allow a remote attacker to bypass TACACS+ authentication of VPN users (the Cisco FWSM only allows VPN sessions for management), firewall sessions, or administrative access to the device.

This vulnerability is documented in Cisco bug ID CSCto74274 ( registered customers only) and has been assigned CVE ID CVE-2011-3298.

SunRPC Inspection Denial of Service Vulnerabilities

The SunRPC inspection engine enables or disables application inspection for the SunRPC protocol. SunRPC is used by Network File System (NFS) and Network Information Service (NIS). SunRPC services can run on any port. When a client attempts to access a SunRPC service on a server, it must learn the port on which the service is running. The client does this by querying the port mapper process, usually rpcbind, on the well-known port of 111.

The Cisco FWSM is affected by four vulnerabilities that may cause the device to reload during the processing of different crafted SunRPC messages when SunRPC inspection is enabled. These vulnerabilities are triggered only by transit traffic; traffic that is destined to the device does not trigger these vulnerabilities.

These vulnerabilities are documented in Cisco bug IDs CSCtq09972 ( registered customers only) , CSCtq09978 ( registered customers only) , CSCtq09986 ( registered customers only) , and CSCtq09989 ( registered customers only) ; and have been assigned Common Vulnerabilities and Exposures (CVE) IDs CVE-2011-3299, CVE-2011-3300, CVE-2011-3301, and CVE-2011-3302, respectively.

ILS Inspection Denial of Service Vulnerability

The ILS inspection engine provides Network Address Translation (NAT) support for Microsoft NetMeeting, SiteServer, and Active Directory products that use Lightweight Directory Access Protocol (LDAP) to exchange directory information with an ILS server.

The Cisco FWSM is affected by a vulnerability when ILS inspection is enabled that may cause the device to reload during the processing of a malformed ILS message. This vulnerability is triggered by transit traffic only; traffic that is destined to the device does not trigger this vulnerability.

This vulnerability is documented in Cisco bug ID CSCtq57802 ( registered customers only) and has been assigned CVE ID CVE-2011-3303.

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.

CSCti83875 -- Syslog message 302015 may lead to memory corruption and CP lockup

Calculate the environmental score of CSCti83875

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

CSCtn15697 -- FWSM crash in thread name uauth

Calculate the environmental score of CSCtn15697

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

CSCto74274 -- Crafted TACACS+ reply considered as successful auth by FWSM

Calculate the environmental score of CSCto74274

CVSS Base Score - 7.9

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Adjacent Network

Medium

None

Complete

Complete

Complete

CVSS Temporal Score - 6.5

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

SunRPC Inspection Denial of Service Vulnerabilities

Calculate the environmental score of CSCtq09972, CSCtq09978, CSCtq09986, CSCtq09989

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

CSCtq57802 -- ILS inspection crash on malformed ILS traffic

Calculate the environmental score of CSCtq57802

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 any of the denial of service vulnerabilities could cause an affected device to reload. Repeated exploitation could result in a sustained denial of service condition.

Successful exploitation of the TACACS+ authentication bypass vulnerability could allow an attacker to bypass authentication of VPN, firewall, and/or administrative sessions.

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 following Cisco FWSM Software table describes a major Cisco FWSM Software train and the earliest possible release in that train that contains the fix (the "First Fixed Release") and the anticipated date of availability (if not currently available) in the First Fixed Release column. A device that is running a release that is earlier than the release in a specific column (earlier than the First Fixed Release) is known to be vulnerable. A vulnerable release should be upgraded to the indicated release at a minimum, or a later version (later than or equal to the First Fixed Release label).

Major Release

First Fixed Release

3.1

3.1(21)

3.2

3.2(22)

4.0

4.0(16)

4.1

4.1(7)

Fixed Cisco FWSM Software can be downloaded from the Software Center on Cisco.com by visiting http://www.cisco.com/cisco/software/navigator.html and navigating to Products > Security > Firewall > Firewall Integrated Switch/Router Services > Cisco Catalyst 6500 Series Firewall Services Module > Firewall Services Module (FWSM) Software.


Workarounds

This Cisco Security Advisory describes multiple distinct vulnerabilities. These vulnerabilities and their respective workarounds are independent of each other.

Syslog Message Memory Corruption Denial of Service Vulnerability

Completely disabling syslog 302015 with the command no logging message 302015 is an effective workaround for this vulnerability.

Authentication Proxy Denial of Service Vulnerability

There are no workarounds available for this vulnerability.

TACACS+ Authentication Bypass Vulnerability

There are no workarounds available for this vulnerability other than using a different authentication protocol such as RADIUS and LDAP.

SunRPC Inspection Denial of Service Vulnerabilities

Administrators can mitigate these vulnerabilities by disabling SunRPC inspection if it is not required. Administrators can disable SunRPC inspection by issuing the no inspect sunrpc command in class configuration sub-mode in the policy map configuration. Disabling SunRPC inspection may cause SunRPC traffic to stop transiting the security appliance.

ILS Inspection Denial of Service Vulnerability

Administrators can mitigate this vulnerability by disabling ILS inspection if it is not required. Administrators can disable ILS inspection by issuing the no inspect ils command in class configuration sub-mode in the policy map configuration. Disabling ILS inspection may cause ILS traffic to stop through the security appliance.

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/en/US/support/tsd_cisco_worldwide_contacts.html 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 Syslog Message Memory Corruption Denial of Service Vulnerability, Authentication Proxy Denial of Service Vulnerability, and TACACS+ Authentication Bypass Vulnerability were discovered during the troubleshooting of customer service requests.

The SunRPC Inspection Denial of Service Vulnerabilities and ILS Inspection Denial of Service Vulnerability 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 Security Intelligence Operations at the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20111005-fwsm

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 1.1 2012-July-14 Updated meta-tags for Affected Products.
Revision 1.0 2011-October-05 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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