Cisco Security Advisory
Cisco ASA 5500 Series Adaptive Security Appliances and Cisco Catalyst 6500 Series ASA Services Module Denial of Service Vulnerability
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AV:N/AC:L/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
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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 software updates that address this vulnerability. Workarounds that mitigate this vulnerability are available. This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120620-asaipv6
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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:
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.ciscoasa# show firewall
Firewall mode: Transparent
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:
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.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 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):
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.ciscoasa#show version | include Version
Cisco Adaptive Security Appliance Software Version 8.4(1)
Device Manager Version 6.4(1)
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.
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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.
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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
[...]
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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
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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.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Show LessRevision 1.0 2012-June-20 Initial public release
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