Cisco Security Advisory
Cisco IOS NAT Skinny Call Control Protocol Vulnerability
AV:N/AC:L/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
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A series of segmented Skinny Call Control Protocol (SCCP) messages may cause a Cisco IOS device that is configured with the Network Address Translation (NAT) SCCP Fragmentation Support feature to reload.
Cisco has released software updates that address this vulnerability. A workaround that mitigates this vulnerability is available.
This advisory is posted at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-sccp.
Note: The September 24, 2008 IOS Advisory bundled publication includes twelve Security Advisories. Eleven of the advisories address vulnerabilities in Cisco's IOS software, and one advisory addresses vulnerabilities in Cisco Unified Communications Manager. Each Advisory lists the releases that correct the vulnerability described in the Advisory.
Individual publication links are listed below:
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-cucm
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-iosfw
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-iosips
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-ipc
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-l2tp
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-mfi
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-multicast
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-sccp
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-sip
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-ssl
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-ubr
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-vpn
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-cucm
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Vulnerable Products
This security advisory applies to all Cisco products that run Cisco IOS Software configured for NAT and that support the NAT SCCP Fragmentation Support feature. This feature was first introduced in Cisco IOS version 12.4(6)T.
To verify if NAT is enabled on a Cisco IOS device log into the device and issue the command show ip nat statistics. The following example shows a device configured with NAT:
Router# show ip nat statistics Total translations: 2 (0 static, 2 dynamic; 0 extended) Outside interfaces: Serial0 Inside interfaces: Ethernet1 Hits: 135 Misses: 5 Expired translations: 2 Dynamic mappings: -- Inside Source access-list 1 pool mypool refcount 2 pool mypool: netmask 255.255.255.0 start 192.168.10.1 end 192.168.10.254 type generic, total addresses 14, allocated 2 (14%), misses 0
Alternatively, you can use the show running-config | include ip nat command to verify if NAT has been enabled on the router interfaces.
Note: With reference to NAT, the term "inside" refers to those networks that will be translated. Inside this domain, hosts will have addresses in one address space, while on the "outside", they will appear to have addresses in another address space when NAT is configured. The first address space is referred to as the local address space and the second is referred to as the global address space. The ip nat inside and ip nat outside interface commands must be present on the corresponding router interfaces in order for NAT to be enabled.
In order to determine the software that runs on a Cisco IOS product, log in to the device and issue the show version command to display the system banner. Cisco IOS software identifies itself as "Internetwork Operating System Software" or simply "IOS." On the next line of output, the image name displays between parentheses, followed by "Version" and the Cisco IOS release name. Other Cisco devices do not have the show version command or give different output.
The following example shows output from a device that runs an IOS image:
router>show version Cisco IOS Software, 7200 Software (C7200-ADVSECURITYK9-M), Version 12.4(6)T2, RELEASE SOFTWARE (fc1) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2006 by Cisco Systems, Inc. Compiled Tue 16-May-06 16:09 by kellythw
Products Confirmed Not Vulnerable
Cisco IOS XR and IOS XE are not affected by this vulnerability.
Cisco IOS devices not explicitly configured for NAT are not vulnerable.
No other Cisco products are currently known to be affected by these vulnerabilities.
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The Skinny Call Control Protocol (SCCP) enables voice communication between an SCCP client and a Call Manager (CM). Typically, the CM provides service to the SCCP clients on TCP Port 2000 by default. Initially, an SCCP client connects to the CM by establishing a TCP connection; the client will also establish a TCP connection with a secondary CM, if available.
The NAT SCCP Fragmentation Support feature prevents skinny control message exchanges from failing in a TCP segmentation scenario because the NAT Skinny Application Layer Gateway (ALG) is able to reassemble the skinny control messages. A segmented payload that requires an IP or port translation will no longer be dropped. The NAT SCCP Fragmentation Support feature was introduced in Cisco IOS version 12.4(6)T.
A series of fragmented SCCP messages may cause a Cisco IOS router that is running the NAT SCCP Fragmentation Support feature to reload.
This vulnerability is documented in Cisco Bug ID CSCsg22426 ( registered customers only) and CSCsi17020 ( registered customers only) , and has been assigned CVE identifiers CVE-2008-3810 and CVE-2008-3811.
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As workaround, an administrator can disable SCCP NAT support using the no ip nat service skinny tcp port 2000 command, as shown in the following example:
Router(config)# no ip nat service skinny tcp port 2000
Note: If your Cisco CallManager is using a TCP port for skinny signaling different from the default port (2000), you need to adjust this command accordingly.
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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 Cisco IOS software table (below) names a Cisco IOS release train. If a given release train is vulnerable, then the earliest possible releases that contain the fix (along with the anticipated date of availability for each, if applicable) are listed in the "First Fixed Release" column of the table. The "Recommended Release" column indicates the releases which have fixes for all the published vulnerabilities at the time of this Advisory. A device running a release in the given train that is earlier than the release in a specific column (less than the First Fixed Release) is known to be vulnerable. Cisco recommends upgrading to a release equal to or later than the release in the "Recommended Releases" column of the table.
Major Release
Availability of Repaired Releases
Affected 12.0-Based Releases
First Fixed Release
Recommended Release
There are no affected 12.0 based releases
Affected 12.1-Based Releases
First Fixed Release
Recommended Release
There are no affected 12.1 based releases
Affected 12.2-Based Releases
First Fixed Release
Recommended Release
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
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Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
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Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Affected 12.3-Based Releases
First Fixed Release
Recommended Release
There are no affected 12.3 based releases
Affected 12.4-Based Releases
First Fixed Release
Recommended Release
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.4(11)MD4
12.4(15)MD1
12.4(16)MR
12.4(19)MR
12.4(15)SW2; Available on 28-SEP-08
12.4(15)SW2; Available on 28-SEP-08
12.4(11)T4
12.4(15)T2
12.4(20)T
12.4(6)T11
12.4(9)T5
12.4(15)T7
Not Vulnerable
Not Vulnerable
Vulnerable; first fixed in 12.4T
12.4(15)T7
Not Vulnerable
Vulnerable; first fixed in 12.4T
12.4(15)T7
Vulnerable; first fixed in 12.4T
12.4(15)T7
12.4(9)XG3
12.4(9)XG3
Vulnerable; first fixed in 12.4T
12.4(15)T7
Vulnerable; first fixed in 12.4T
12.4(15)T7
12.4(15)XL2
12.4(15)XL2
12.4(15)XM1
12.4(15)XM1
Vulnerable; contact TAC
Vulnerable; contact TAC
Not Vulnerable
Not Vulnerable
Vulnerable; first fixed in 12.4T
12.4(15)T7
Vulnerable; contact TAC
12.4(11)XW7
12.4(11)XW9
Not Vulnerable
Not Vulnerable
Not Vulnerable
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The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.
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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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Revision 1.1
2009-April-16
Removed references to the combined software table, as it is now outdated
Revision 1.0
2008-September-24
Initial public release
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