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Cisco ASA 5500 Series Adaptive Security Appliances and Cisco Catalyst 6500 Series ASA Services Module Denial of Service Vulnerability

Advisory ID: cisco-sa-20120620-asaipv6

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120620-asaipv6

Revision 1.0

For Public Release 2012 June 20 16:00  UTC (GMT)


Summary

Cisco ASA 5500 Series Adaptive Security Appliances (Cisco ASA) and Cisco Catalyst 6500 Series ASA Services Module (Cisco ASASM) contain a vulnerability that may allow an unauthenticated, remote attacker to cause the reload of the affected device.

Cisco has released free software updates that address this vulnerability. Workarounds that mitigate this vulnerability are available. This advisory is available at the following link:
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120620-asaipv6

Affected Products

Cisco ASA and Cisco ASASM are affected by this vulnerability. Not all the versions of Cisco ASA Software are affected by this vulnerability. Consult the "Software Versions and Fixes" section of this security advisory for more information about the affected version.

Vulnerable Products

For specific version information, refer to the "Software Versions and Fixes" section of this advisory.

Cisco ASA and Cisco ASASM contain a vulnerability that may allow an unauthenticated, remote attacker to cause the reload of the affected device.

Cisco ASA Software may be affected by this vulnerability if all the following conditions are present:
  • Cisco ASA or Cisco ASASM is running in transparent firewall mode
  • Cisco ASA or Cisco ASASM has IPv6 enabled
  • Cisco ASA or Cisco ASASM has system logging enabled and the system is configured to log message ID 110003

To verify that the Cisco ASA or Cisco ASASM is running in transparent firewall mode, issue the show firewall command. The following example shows a Cisco ASA running in transparent firewall mode:

ciscoasa# show firewall
Firewall mode: Transparent
IPv6 is not enabled by default. In order to enable IPv6 on a Cisco ASA or Cisco ASASM configured in transparent firewall mode at a minimum a link-local address needs to be configured for IPv6 to operate correctly. If a global address is configured, a link-local address is automatically configured on each interface.

To verify that the Cisco ASA or Cisco ASASM has IPv6 enabled, issue the show ipv6 interface command and confirm that the command returns output. The following example shows a Cisco ASA configured with two interfaces (inside and outside) running in transparent firewall mode and IPv6 enabled:

ciscoasa# show ipv6 interface
outside is up, line protocol is up
  IPv6 is enabled, link-local address is fe80::219:2fff:fe83:4f42
  No global unicast address is configured
  Joined group address(es):
    ff02::1
    ff02::1:ff83:4f42
  ICMP error messages limited to one every 100 milliseconds
  ICMP redirects are enabled
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds
  ND advertised retransmit interval is 1000 milliseconds
  Hosts use stateless autoconfig for addresses.
inside is up, line protocol is up
  IPv6 is enabled, link-local address is fe80::219:2fff:fe83:4f43
  No global unicast address is configured
  Joined group address(es):
    ff02::1
    ff02::1:ff83:4f43
  ICMP error messages limited to one every 100 milliseconds
  ICMP redirects are enabled
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds
  ND advertised retransmit interval is 1000 milliseconds
  Hosts use stateless autoconfig for addresses.
Syslog message ID 110003 is generated when the Cisco ASA is unable to find the next hop on an interface routing table. Additional information regarding this syslog message can be found in the Cisco ASA System Log Messages guide at: http://www.cisco.com/en/US/products/ps6120/products_system_message_guides_list.html. Logging is not enabled by default on a Cisco ASA; however, when logging is enabled a Cisco ASA will automatically enable syslog message 110003.

Syslog message 110003 has a default severity level of 6 (informational). Cisco ASA Software configured for logging at Level 6 or higher (that is Levels 6 through 7) may be vulnerable.
To verify if logging is enabled, issue the show logging command. The following example shows a Cisco ASA with logging enabled and buffer logging enabled at Level 6 (informational):
ciscoasa# show logging
Syslog logging: enabled
Facility: 20
Timestamp logging: disabled
Standby logging: disabled
Debug-trace logging: disabled
Console logging: disabled
Monitor logging: disabled
Buffer logging: level informational, 2 messages logged
Trap logging: disabled
Permit-hostdown logging: disabled
History logging: disabled
Device ID: disabled
Mail logging: disabled
ASDM logging: disabled

Using a custom message list (created via the logging list command) that includes syslog message 110003, either by severity or by explicitly including the message ID, is also a vulnerable configuration.

The default severity level of syslog messages can be changed. If the default severity level of syslog message 110003 is changed and the device is configured to log to any destination at the new severity level, the device is vulnerable.

Determine the Running Software Version

To determine whether a vulnerable version of Cisco ASA Software is running on an appliance, administrators can issue the show version command. The following example shows a Cisco ASA 5500 Series Adaptive Security Appliance that is running software version 8.4(1):
ciscoasa#show version | include Version
Cisco Adaptive Security Appliance Software Version 8.4(1)
Device Manager Version 6.4(1)
Customers who use Cisco Adaptive Security Device Manager (ASDM) to manage devices can locate the software version in the table that is displayed in the login window or upper-left corner of the Cisco ASDM window.

Information about Cisco PIX Security Appliance

Cisco PIX is not affected by the vulnerability described in this security advisory. Cisco PIX has reached end of maintenance support. Cisco PIX customers are encouraged to migrate to Cisco ASA.

Products Confirmed Not Vulnerable

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

Details

Cisco ASA 5500 Series Adaptive Security Appliances (Cisco ASA) and Cisco Catalyst 6500 Series ASA Services Module (Cisco ASASM) contain a vulnerability that may allow an unauthenticated, remote attacker to cause a reload of the affected device.

Note:
This vulnerability can only be triggered by IPv6 transit traffic, and affects both Cisco ASA and Cisco ASASM when configured in transparent firewall mode (either single or multiple context mode).

This vulnerability is documented in Cisco bug ID CSCua27134 (registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2012-3058.

Vulnerability Scoring Details

Cisco has scored the vulnerabilities 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



CSCua27134 - Cisco ASA IPv6 Packets Denial of Service Vulnerability

Calculate the environmental score of CSCua27134

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 this vulnerability may result in a reload of the affected device. Repeated exploit attempts may result in a sustained denial of service (DoS) attack.

Software Versions and Fixes

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

Vulnerability Major Release
First Fixed Release
Cisco ASA IPv6 Packets Denial Of Service Vulnerability
7.0 Not Affected
7.1 Not Affected
7.2 Not Affected
8.0 Not Affected
8.1 Not Affected
8.2 Not Affected
8.3 Not Affected
8.41 8.4(4.1)
8.5 8.5(1.11); Available July 2012
8.6 8.6 (1.3); Available July 2012

1This vulnerability was introduced in 8.4(2). Versions prior to 8.4(2) are not affected by this vulnerability

Workarounds

A valid workaround is to prevent the Cisco ASA from generating the syslog message 110003. Use the no logging message 110003 command to disable syslog message 110003.

To verify that the message is not being generated issue show running-configuration logging command. The following example shows the output of the command when the logging of message 110003 is disabled:

ciscoasa# show run logging
[...]
no logging message 110003
[...]

Obtaining Fixed Software

Cisco has released free software updates that address the vulnerability 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 Navigator on Cisco.com at http://www.cisco.com/cisco/software/navigator.html.

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 Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

This vulnerability was discovered during the resolution of a service request.

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 at the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120620-asaipv6

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 1.0 2012-June-20 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.