Summary

• Cisco devices running an affected version of Internetwork Operating System (IOS) which supports Session Initiation Protocol (SIP) are affected by a vulnerability that may lead to a reload of the device when receiving a specific series of packets destined to port 5060. This issue is compounded by a related bug which allows traffic to TCP 5060 and UDP port 5060 on devices not configured for SIP.

  There are no known instances of intentional exploitation of this issue. However, Cisco has observed data streams that appear to be unintentionally triggering the vulnerability.

  Workarounds exist to mitigate the effects of this problem on devices which do not require SIP.

  This advisory is posted at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20070131-sip.

Affected Products

• Vulnerable Products

  Any Cisco device which runs a vulnerable version of IOS and supports SIP processing could be vulnerable. This includes IOS versions 12.3(4)XH, 12.3(4)XQ, 12.3(7)XR, 12.3(7)XS, 12.3(8)JA, 12.3(8)T, 12.3(8)XU, 12.3(8)XW, 12.3(8)XX, 12.3(8)XY, 12.3(8)YA, 12.3(8)YG, 12.3(8)YH, 12.3(8)YI, 12.3(8)ZA, 12.4 Mainline and 12.4T onward. Routers configured as SIP Public Switched Telephone Network (PSTN) Gateways are vulnerable, as are routers configured as SIP Session Border Controllers (SBCs) and the CAT6000-CMM card.

  To determine if your device has SIP enabled, enter the commands show ip sockets and show tcp brief all. Below is an example of a router running code without the fix, and without the workaround enabled. The router in this example is running the vulnerable image c7200-p-mz.124-3.bin:

  Router#show ip sockets
  Proto    Remote      Port      Local       Port  In Out Stat TTY OutputIF
  17 0.0.0.0             0  --any--          5060   0   0  211   0
  17 0.0.0.0             0 192.168.100.2       67   0   0 2211   0
  17 0.0.0.0             0 192.168.100.2     2517   0   0   11   0

  The first line with UDP Port 5060 shows that UDP SIP is enabled.

  Router#show tcp brief all
  TCB       Local Address           Foreign Address        (state)
  2051E680  *.5060                  *.*                    LISTEN
  

  The above lines with *.5060 show that TCP SIP is enabled.

  Products Confirmed Not Vulnerable

  Devices that do not support SIP processing are not affected by this issue. This includes but is not limited to the 6500, 7600, 10000 series and 12000 series. To confirm that a device is not vulnerable to this issue, ensure that ports TCP 5060 and UDP 5060 are not open on the device with the commands show tcp brief all and show ip sockets. Below is an example of a router running the fixed image c7200-js-mz.124-5b.bin which is not vulnerable to this issue.

  Router#show tcp brief all
  
  Router#show ip sockets
  Proto    Remote      Port      Local       Port  In Out Stat TTY OutputIF
  17 0.0.0.0             0 192.168.100.2      67   0   0 2211   0

  No lines with UDP Port 5060 are shown and UDP SIP is not enabled. In this example, UDP port 67 is used by DHCP which is not related to this vulnerability.

Details

• SIP is a protocol designed for use in IP voice networks and is widely used for Voice over Internet Protocol (VoIP) communications worldwide.

  Cisco devices running certain versions of IOS with support for SIP services may be affected by a vulnerability that leads to a reload of the device with a crafted series of SIP packets to either TCP port 5060 or UDP port 5060. This vulnerability affects routers that contain any SIP configuration, including SIP gateways. This issue is being tracked as Cisco Bug ID CSCsh58082 ( registered customers only) .

  In addition, certain versions of IOS with support for SIP services may process SIP messages even if they are not configured for SIP operation. To process SIP messages IOS will open UDP port 5060 and TCP port 5060 for listening. The Cisco Bug ID that documents the issue of IOS processing SIP messages without being configured for SIP operation is CSCsb25337 ( registered customers only) . The fix for this bug turns off the listening ports TCP 5060 and UDP 5060.

  A device must have an open SIP port to be vulnerable to this issue. Devices which do not listen on TCP 5060 or UDP 5060 are not vulnerable. Because SIP utilizes UDP as a transport, it is possible to spoof the sender's IP address, which may defeat ACLs that permit communication to these ports from trusted IP addresses.

Workarounds

• Additional mitigations that can be deployed on Cisco devices within the network are available in the Cisco Applied Mitigation Bulletin companion document for this advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20070131-sip.

  Disable SIP listening ports

  For devices which do not require SIP to be enabled, the simplest and most effective workaround is to disable SIP processing on the device with the following commands.

  Warning: When applying this workaround to devices which are processing MGCP or H.323 calls, the device will not allow you to stop SIP processing while active calls are being processed. Under these circumstances, this workaround should be implemented during a maintenance window when active calls can be briefly stopped.

  Enter configuration commands, one per line.  End with CNTL/Z.
  Router(config)#sip-ua
  Router(config-sip-ua)#no transport udp
  Router(config-sip-ua)#no transport tcp
  Router(config-sip-ua)#end
  

  After applying this workaround the commands show ip sockets and show tcp brief all will not show the device listening on UDP and TCP port 5060:

  Router#show ip sockets
  Proto    Remote      Port      Local       Port  In Out Stat TTY
   17   --listen--          9.13.32.18       2887   0   0   11   0
  
  Router#show tcp brief all
  TCB       Local Address           Foreign Address        (state)
  6649A5A4  *.1720                  *.*                    LISTEN
  66CDC764  *.1723                  *.*                    LISTEN

  Control Plane Policing

  For devices which do not need to run SIP, you can use Control Plane Policing (CoPP) to block all SIP access to the device. Cisco IOS software releases 12.0S, 12.2SX, 12.2S, 12.3T, 12.4, and 12.4T support the CoPP feature. CoPP may be configured on a device to protect the management and control planes to minimize the risk and effectiveness of direct infrastructure attacks by explicitly permitting only authorized traffic sent to infrastructure devices in accordance with existing security policies and configurations. The following example can be adapted to your network.

  Warning: Because SIP utilizes UDP as a transport, it is possible to spoof the sender's IP address, which may defeat ACLs that permit communication to these ports from trusted IP addresses.

  
  !-- Permit all TCP and UDP SIP traffic sent to all IP addresses
  !-- configured on all interfaces of the affected device so that it
  !-- will be policed and dropped by the CoPP feature.
  
  
  access-list 100 permit tcp any any eq 5060
  access-list 100 permit udp any any eq 5060
  
  
  !-- Permit (Police or Drop)/Deny (Allow) all other Layer3 and Layer4
  !-- traffic in accordance with existing security policies and
  !-- configurations for traffic that is authorized to be sent
  !-- to infrastructure devices.
  
  
  
  !-- Create a Class-Map for traffic to be policed by
  !-- the CoPP feature.
  
  
  class-map match-all drop-sip-class
    match access-group 100
  
  
  !-- Create a Policy-Map that will be applied to the
  !-- Control-Plane of the device.
  
  
  policy-map drop-sip-traffic
    class drop-sip-class
      drop
  
  
  !-- Apply the Policy-Map to the Control-Plane of the
  !-- device.
  
  
  control-plane
    service-policy input drop-sip-traffic

  In the above CoPP example, the access control list entries (ACEs) which match the potential exploit packets with the "permit" action result in these packets being discarded by the policy-map "drop" function, while packets that match the "deny" action (not shown) are not affected by the policy-map drop function. Additional information on the configuration and use of the CoPP feature can be found at http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6586/ps6642/prod_white_paper0900aecd804fa16a.html and http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gtrtlimt.html.

Fixed Software

• 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) describes a release train and the platforms or products for which it is intended. If a given release train is vulnerable, then the earliest possible releases that contain the fix (the "First Fixed Release") and the anticipated date of availability for each are listed in the "Rebuild" and "Maintenance" columns. 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. The release should be upgraded at least to the indicated release or a later version (greater than or equal to the First Fixed Release label).

  For more information on the terms "Rebuild" and "Maintenance," consult the following URL: http://www.cisco.com/web/about/security/intelligence/ios-ref.html.

  The following table is written to indicate the vulnerable and fixed status of CSCsh58082 ( registered customers only) , which is the bug responsible for the device reload. This table also contains information about IOS releases that are fixed for CSCsb25337 ( registered customers only) , which turns off processing of SIP messages when the device is not fully configured for SIP operation. At the time of the 2.0 publishing, there are no fixes for CSCsh58082 ( registered customers only) .

  Major Release	Availability of Repaired Releases
  Affected 12.0-Based Release	Rebuild	Maintenance
  12.0	All 12.0 releases are not vulnerable
  Affected 12.1-Based Release	Rebuild	Maintenance
  12.1	All 12.1 releases are not vulnerable
  Affected 12.2-Based Release	Rebuild	Maintenance
  12.2	All 12.2 releases are not vulnerable
  Affected 12.3-Based Release	Rebuild	Maintenance
  12.3	Not vulnerable
  12.3B	Not vulnerable
  12.3BC	Not vulnerable
  12.3BW	Not vulnerable
  12.3JA	Not vulnerable
  12.3JEA	Not vulnerable
  12.3JK	Not vulnerable
  12.3JX	Not vulnerable
  12.3T	Vulnerable in all 12.3(8)T and later releases
  12.3TPC	Not vulnerable
  12.3XA	Not vulnerable
  12.3XB	Not vulnerable
  12.3XC	Not vulnerable
  12.3XD	Not vulnerable
  12.3XE	Not vulnerable
  12.3XF	Not vulnerable
  12.3XG	Not vulnerable
  12.3XH	Vulnerable
  12.3XI	Not vulnerable
  12.3XJ	Not vulnerable
  12.3XK	Not vulnerable
  12.3XQ	Vulnerable
  12.3XR	Vulnerable
  12.3XS	Not vulnerable
  12.3XU	Vulnerable
  12.3XW	SIP ports are closed by default in 12.3(14)YX2 or later, but routers running SIP are still vulnerable
  12.3XX	SIP ports are closed by default in 12.3(8)XX2 or later, but routers running SIP are still vulnerable
  12.3XY	Vulnerable
  12.3YA	Not vulnerable
  12.3YD	Not vulnerable
  12.3YF	SIP ports are closed by default in 12.3(14)YX2 or later, but routers running SIP are still vulnerable
  12.3YG	SIP ports are closed by default in 12.3(8)YG5 or later, but routers running SIP are still vulnerable
  12.3YH	Not vulnerable
  12.3YI	Not vulnerable
  12.3YJ	Not vulnerable
  12.3YK	Vulnerable
  12.3YM	SIP ports are closed by default in 12.3(14)YM8 or later, but routers running SIP are still vulnerable
  12.3YQ	Vulnerable
  12.3YS	Not vulnerable
  12.3YT	Vulnerable
  12.3YU	Vulnerable
  12.3YX	SIP ports are closed by default in 12.3(14)YX2 or later, but routers running SIP are still vulnerable
  12.3YZ	Vulnerable
  Affected 12.4-Based Release	Rebuild	Maintenance
  12.4	SIP ports are closed by default in a release listed below, but routers running SIP are still vulnerable
  	12.4(3d)
  	12.4(5b)
  	12.4(7a)	12.4(8)
  12.4MR	SIP ports are closed by default in 12.4(6)MR or later, but routers running SIP are still vulnerable
  12.4SW	Vulnerable; workaround available for all 12.4SW releases where SIP ports are closed by default
  12.4T	SIP ports are closed by default in a release listed below, but routers running SIP are still vulnerable
  	12.4(2)T5
  	12.4(4)T3
  	12.4(6)T1	12.4(9)T
  12.4XA	Vulnerable
  12.4XB	SIP ports are closed by default in 12.4(4)XB2 or later, but routers running SIP are still vulnerable
  12.4XC	SIP ports are closed by default in 12.4(4)XC6* available 12-Feb-07; but routers running SIP are still vulnerable
  12.4XD	SIP ports are closed by default in 12.4(4)XD2 or later, but routers running SIP are still vulnerable
  12.4XE	Vulnerable; workaround available for all 12.4XE releases where SIP ports are closed by default
  12.4XG	Not vulnerable
  12.4XJ	Vulnerable; workaround available for all 12.4XJ releases where SIP ports are closed by default
  12.4XP	Vulnerable; workaround available for all 12.4XP releases where SIP ports are closed by default
  12.4XT	Vulnerable; workaround available for all 12.4XT releases where SIP ports are closed by default

Exploitation and Public Announcements

• This issue was first reported to Cisco by a customer. There are no known instances of intentional exploitation of this issue. However, Cisco has observed data streams that appear to be unintentionally triggering the vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20070131-sip

Revision History

• Revision 2.1	2007-February-10	Changed formatting and wording of advisory table.
  Revision 2.0	2007-February-9	Updated document to reflect that all products with open ports 5060 are vulnerable. Updated Vulnerable Products with voice gateways, SBCs, and CAT6000-CMM. Updated the software table to reflect vulnerability of 12.3(4)XH, 12.3(4)XQ, 12.3(7)XR, 12.3(7)XS, 12.3(8)JA, 12.3(8)XU, 12.3(8)XW, 12.3(8)XX, 12.3(8)XY, 12.3(8)YA, 12.3(8)YH, 12.3(8)YI and 12.3(8)ZA.
  Revision 1.1	2007-January-31	Added Common Vulnerability Scoring System (CVSS) scoring for all bugs mentioned in the advisory. Added CSCsh58082 ( registered customers only) as the Cisco Bug ID that tracks the root cause of the vulnerability. Minor wording changes.
  Revision 1.0	2007-January-31	Initial public release.

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