Cisco Security Advisory

Multiple Vulnerabilities in Cisco Firewall Services Module

Advisory ID: cisco-sa-20100804-fwsm

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100804-fwsm

Revision 1.0

For Public Release 2010 August 4 16:00  UTC (GMT)


Summary

Multiple vulnerabilities exist in the Cisco Firewall Services Module (FWSM) for the Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers that may cause the Cisco FWSM to reload after processing crafted SunRPC or certain TCP packets. Repeated exploitation could result in a sustained DoS condition.

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

Note:  These vulnerabilities are independent of each other. A device may be affected by one vulnerability and not affected by another.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100804-fwsm.

Note:  The Cisco ASA 5500 Series Adaptive Security Appliances are affected by the SunRPC inspection vulnerabilities described in this advisory. A separate Cisco Security Advisory has been published to disclose this and other vulnerabilities that affect the Cisco ASA 5500 Series Adaptive Security Appliances. The advisory is available at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100804-asa.

Affected Products

Vulnerable Products

The Cisco Firewall Services Module (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.

SunRPC Inspection Denial of Service Vulnerabilities

Cisco FWSM Software version 3.x and 4.x are affected by these vulnerabilities only if SunRPC inspection is enabled. SunRPC inspection is enabled by default.

To check if SunRPC inspection is enabled, use the show service-policy | include sunrpc command and confirm that the command returns output, as shown in the following example:

fwsm#show service-policy | include sunrpc
      Inspect: sunrpc , packet 0, drop 0, reset-drop 0

Alternatively, a device that has SunRPC inspection enabled has a configuration similar to the following:

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

Note:  The Cisco ASA 5500 Series Adaptive Security Appliances are affected by the SunRPC inspection vulnerabilities described in this advisory. A separate Cisco Security Advisory has been published to disclose this and other vulnerabilities that affect the Cisco ASA 5500 Series Adaptive Security Appliances. The advisory is available at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100804-asa.

TCP Denial of Service Vulnerability

Cisco FWSM Software version 3.x and 4.x are affected by this vulnerability when configured in multi-mode (with virtual firewalls) and with any of the following features:

  • ASDM Administrative Access
  • Telnet
  • SSH

To verify if the FWSM is running in multiple mode, use the show mode command, as shown in the following example:

FWSM(config)#show mode
Security context mode: multiple
The flash mode is the SAME as the running mode.

The following commands are used to enable the HTTPS server and allow only hosts on the inside interface with an address in the 192.168.1.0/24 network to create ASDM, SSH or Telnet connections:

asa(config)# http server enable
asa(config)# http 192.168.1.0 255.255.255.0 inside
asa(config)# telnet 192.168.1.0 255.255.255.0 inside
asa(config)# ssh 192.168.1.0 255.255.255.0 inside

Determining Software Versions

To determine the version of Cisco FWSM Software that is running, issue the show module command from Cisco IOS Software or Cisco Catalyst Operating System Software to identify what modules and sub modules 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)       8.5(0.46)RFW Ok
  2  0018.ba41.5092 to 0018.ba41.5099   4.0   7.2(1)       3.2(2)10     Ok
  3  0014.a90c.9956 to 0014.a90c.995d   5.0   7.2(1)       5.1(6)E1     Ok
  4  0014.a90c.66e6 to 0014.a90c.66ed   1.7                4.2(3)       Ok
  5  0013.c42e.7fe0 to 0013.c42e.7fe3   4.4   8.1(3)       12.2(18)SXF1 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)       3.2(2)10     Ok

[...]

The preceding example shows that the FWSM is running software version 3.2(2)10 as indicated by the column under "Sw."

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 the 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 FWSM through the show version command, as shown in the following example:

FWSM> show version
FWSM Firewall Version 3.2(2)10 
[...]

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 ASDM window. The version notation is similar to the following example.

FWSM Version: 3.2(2)10

Products Confirmed Not Vulnerable

With the exception of Cisco ASA 5500 Series Adaptive Security Appliances, 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.

SunRPC Inspection Denial of Service Vulnerabilities

The Cisco FWSM is affected by three vulnerabilities that may cause the device to reload during the processing of different crafted SunRPC messages when SunRPC inspection is enabled.

Note:  These vulnerabilities are only triggered by transit traffic; traffic that is destined to the device does not trigger these vulnerabilities.

These vulnerabilities are documented in Cisco bug IDs CSCte61710 ( registered customers only) , CSCte61622 ( registered customers only) , and CSCte61662 ( registered customers only) ; and have been assigned Common Vulnerabilities and Exposures (CVE) IDs CVE-2010-2818, CVE-2010-2819, and CVE-2010-2820, respectively.

TCP Denial of Service Vulnerability

You can partition a single FWSM into multiple virtual devices, known as security contexts. Each context has its own security policy, interfaces, and administrators. Multiple contexts are similar to multiple standalone devices. Many features are supported in multiple context mode, which includes routing tables, firewall features, and management.

Cisco FWSM is affected by a denial of service vulnerability that could allow an unauthenticated attacker to cause a reload when sending a series of TCP packets. The Cisco FWSM is only affected by this vulnerability when is configured in multi-mode (with virtual firewalls) and configured to accept Telnet, SSH or ASDM connections.

Note:  A TCP three-way handshake is needed to exploit this vulnerability. This vulnerability is only triggered by traffic that is destined to the affected device; transit traffic does not trigger this vulnerability.

This vulnerability is documented in Cisco bug ID CSCtg68694 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2010-2821.

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

CSCte61710, CSCte61622, CSCte61662 - Passthrough traffic crashes FWSM with SunRPC inspection

Calculate the environmental score of CSCte61710, CSCte61622, CSCte61662

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

CSCtg68694 - FWSM may crash with certain TCP sessions in multiple mode

Calculate the environmental score of CSCtg68694

CVSS Base Score - 7.1

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Medium

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

Impact

Successful exploitation of all the vulnerabilities described in this security advisory may cause a reload of the affected appliance. Repeated exploitation could result in a sustained DoS condition.

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.

Vulnerability

Major Release

First Fixed Release

SunRPC Inspection Denial of Service Vulnerabilities (CSCte61710, CSCte61622, and CSCte61662)

3.1

3.1(17.2)

3.2

3.2(16.1)

4.0

4.0(10.1)

4.1

4.1(1.1)

TCP Denial of Service Vulnerability (CSCtg68694)

3.1

Not vulnerable

3.2

3.2(17.2)

4.0

4.0(11.1)

4.1

4.1(1.2)

Recommended Releases

The following table lists all recommended releases. These recommended releases contain the fixes for all vulnerabilities in this advisory. Cisco recommends upgrading to a release that is equal to or later than these recommended releases.

Major Release

Recommended Release

3.1

3.1(18)

3.2

3.2(18)

4.0

4.0(12)

4.1

4.1(2)

Software Download

Fixed Cisco FWSM Software can be downloaded from the Software Center on Cisco.com by visiting http://www.cisco.com/cisco/web/download/index.html and navigating to Security > Cisco Catalyst 6500 Series Firewall Services Module > Firewall Services Module (FWSM) Software.


Workarounds

The SunRPC inspection vulnerabilities can be mitigated 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 within policy-map configuration.

The TCP DoS vulnerability can be mitigated by only allowing trusted hosts to communicate with the FWSM via HTTPs, SSH, or Telnet. For example, the following commands are used to enable the HTTPS server and allow only hosts on the inside interface with an address in the 192.168.1.0/24 network to create ASDM, SSH or Telnet connections:

asa(config)# http server enable
asa(config)# http 192.168.1.0 255.255.255.0 inside
asa(config)# telnet 192.168.1.0 255.255.255.0 inside
asa(config)# ssh 192.168.1.0 255.255.255.0 inside

Additional mitigation techniques that can be deployed on Cisco devices within the network are available in the Cisco Applied Mitigation Bulletin companion document for this advisory: http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20100804-fwsm.

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 vulnerability described in this advisory.

These vulnerabilities were found during the troubleshooting of customer service requests and 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-20100804-fwsm

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-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
  • 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

2010-August-04

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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