Cisco IOS Software Session Initiation Protocol Denial of Service Vulnerability

Summary

• A vulnerability in the Session Initiation Protocol (SIP) implementation in Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a reload of an affected device. To exploit this vulnerability, affected devices must be configured to process SIP messages.
  
  Cisco has released software updates that address this vulnerability.
  
  There are no workarounds for devices that must run SIP; however, mitigations are available to limit exposure to this vulnerability.
  
  This advisory is available at the following link:
  http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20140924-sip
  
  Note: The September 24, 2014, Cisco IOS Software Security Advisory bundled publication includes six Cisco Security Advisories. All advisories address vulnerabilities in Cisco IOS Software. Individual publication links are in Cisco Event Response: Semiannual Cisco IOS Software Security Advisory Bundled Publication at the following link:

  http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_sep14.html

Affected Products

• Vulnerable Products

  Cisco devices are affected when running an affected Cisco IOS Software or Cisco IOS XE Software release and configured to process SIP messages. Because there are several ways that a device running Cisco IOS Software or Cisco IOS XE Software can start processing SIP messages, it is recommended to use the commands show udp | include 5060 and show tcp brief all | include 5060|5061 to determine whether the SIP ports are open. By default, SIP runs on UDP or TCP port 5060 and runs on TCP port 5061 when Transport Layer Security (TLS) is used. If the output of the commands is not empty, the ports are open and the device is vulnerable, as the following example illustrates:

  Router# show udp | include 5060
   17     0.0.0.0             0 --any--          5060   0   0    11   0 
  
  Router# show tcp brief all | include 5060|5061
  7F1277405E20  0.0.0.0.5061               *.*                         LISTEN
  7F127BBE20D8  0.0.0.0.5060               *.*                         LISTEN
  

  Note: if the port for SIP or secure SIP has been changed from the default, the previous example should reference the new port in use.
  
  

  To determine the Cisco IOS Software release that is running on a Cisco product, administrators can log in to the device and issue the show version command to display the system banner. The system banner confirms that the device is running Cisco IOS Software by displaying text similar to "Cisco Internetwork Operating System Software" or "Cisco IOS Software." The image name displays in parentheses, followed by "Version" and the Cisco IOS Software release name. Other Cisco devices do not have the show version command or may provide different output.

  The following example identifies a Cisco product that is running Cisco IOS Software Release 15.2(4)M5 with an installed image name of C3900-UNIVERSALK9-M:

  Router> show version 
  Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), 15.2(4)M5, RELEASE SOFTWARE (fc2)
  Technical Support: http://www.cisco.com/techsupport
  Copyright (c) 1986-2013 by Cisco Systems, Inc.
  Compiled Fri 13-Sep-13 16:44 by prod_rel_team

  !--- output truncated 

  Additional information about Cisco IOS Software release naming conventions is available in White Paper: Cisco IOS and NX-OS Software Reference Guide.

  Products Confirmed Not Vulnerable

  Cisco Unified Communications Manager is not affected by this vulnerability.
  
  No other Cisco products are currently known to be affected by this vulnerability.

Details

• SIP is a popular signaling protocol that is used to manage voice and video calls across IP networks such as the Internet. SIP is responsible for handling all aspects of call setup and termination. Voice and video are the most popular types of sessions that SIP handles, but the protocol has the flexibility to accommodate other applications that require call setup and termination. SIP call signaling can use UDP port 5060, TCP port 5060, or TLS on TCP port 5061 as the underlying transport protocol.
  
  A vulnerability in the Session Initiation Protocol (SIP) implementation in Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a reload of an affected device.
  
  The vulnerability is due to incorrect processing of specific SIP messages. An attacker could exploit this vulnerability by sending a crafted SIP message on an established call or initiating a call that includes the crafted SIP message, which would trigger a device reload. Only traffic destined to the device can trigger the vulnerability; transit SIP traffic is not an exploit vector. This vulnerability can be exploited with SIP over IP version 4 (IPv4) or IP version 6 (IPv6) communications protocol. This vulnerability can be exploited with SIP over UDP traffic or SIP over TCP traffic.
  
  This vulnerability is documented in Cisco bug ID CSCul46586 (registered customers only). This vulnerability has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2014-3360.

Workarounds

• If the affected Cisco device running Cisco IOS Software or Cisco IOS XE Software requires SIP for VoIP services, SIP cannot be disabled, and no workarounds are available. Users are advised to apply mitigation techniques to help limit exposure to the vulnerability. Mitigation consists of allowing only legitimate devices to connect to affected devices. To increase effectiveness, the mitigation must be coupled with antispoofing measures on the network edge. This action is required because SIP can use UDP as the transport protocol.
  
  Additional mitigations that can be deployed on Cisco devices within the network are available in the Applied Mitigation Bulletin companion document Identifying and Mitigating Exploitation of the Cisco IOS Software Session Initiation Protocol Denial of Service Vulnerability, which is available at the following link: http://tools.cisco.com/security/center/viewAMBAlert.x?alertId=35259

  Disabling SIP Listening Ports

  For devices that do not require SIP to be enabled, the simplest and most effective workaround is to disable SIP processing on the device. Some releases of Cisco IOS Software and Cisco IOS XE Software allow administrators to disable SIP with the following commands:

  sip-ua
   no transport udp
   no transport tcp
   no transport tcp tls
  

  Warning: When applying this workaround to devices that are processing Media Gateway Control Protocol (MGCP) or H.323 calls, the device will not 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 stopped briefly.
  
  The show udp and show tcp brief all commands can be used to confirm that the SIP UDP and TCP ports are closed after applying this workaround.
  
  Depending on the Cisco IOS Software release in use, when SIP is disabled the output from the show ip sockets command may still show the SIP ports open, but sending traffic to them will cause the SIP process to display the following message:

  *Nov 2 11:36:47.691: sip_udp_sock_process_read: SIP UDP Listener is DISABLED

  Control Plane Policing

  For devices that need to offer SIP services, it is possible to use Control Plane Policing (CoPP) to block SIP traffic to the device from untrusted sources. Cisco IOS Software and Cisco IOS XE Software releases 12.0S, 12.2SX, 12.2S, 12.3T, 12.4, 12.4T and newer 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 specific network configurations:

  !- The 192.168.1.0/24 network and the 172.16.1.1 host are trusted.
  !- Everything else is not trusted. The following access list is used
  !- to determine which traffic needs to be dropped by a control plane
  !- policy (the CoPP feature): if the access list matches (permit),
  !- traffic will be dropped and if the access list does not
  !- match (deny), traffic will be processed by the router.
  
  access-list 100 deny udp 192.168.1.0 0.0.0.255 any eq 5060
  access-list 100 deny tcp 192.168.1.0 0.0.0.255 any eq 5060
  access-list 100 deny tcp 192.168.1.0 0.0.0.255 any eq 5061
  access-list 100 deny udp host 172.16.1.1 any eq 5060
  access-list 100 deny tcp host 172.16.1.1 any eq 5060
  access-list 100 deny tcp host 172.16.1.1 any eq 5061
  access-list 100 permit udp any any eq 5060
  access-list 100 permit tcp any any eq 5060
  access-list 100 permit tcp any any eq 5061
  
  !- 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 control-plane-policy
   class drop-sip-class
    drop
  
  !- Apply the policy map to the control plane of the
  !- device.
  
  control-plane
   service-policy input control-plane-policy

  Note: Because SIP can use UDP as a transport protocol, it is possible to spoof the source address of an IP packet, which may bypass access control lists that permit communication to these ports from trusted IP addresses. Information about Unicast Reverse Path Forwarding to help prevent spoofing is available at Understanding Unicast Reverse Path Forwarding.
  
  In the preceding CoPP example, the access control entries that match the potential exploit packets with the permit action cause these packets to be discarded by the policy map drop function, while packets that match the deny action are not affected by the policy map drop function. Additional information about the configuration and use of the CoPP feature is available at Control Plane Policing Implementation Best Practices and the Control Plane Policing chapter of the QoS Policing and Shaping Configuration Guide.

Fixed Software

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

  Cisco IOS Software

  Cisco has provided a tool to help customers determine their exposure to vulnerabilities in Cisco IOS Software. The Cisco IOS Software Checker allows customers to perform the following tasks:

  • Initiate a search by selecting releases from the drop-down menu or uploading a file from a local system
  • Enter show version command output for the tool to parse
  • Create a customized search by including all previously published Cisco Security Advisories, a specific publication, or all advisories in the September 2015 bundled publication

  The tool will identify any Cisco Security Advisories that impact a queried software release and the earliest release that corrects all vulnerabilities in each Cisco Security Advisory ("First Fixed"). If applicable, the tool will also return the earliest possible release that corrects all vulnerabilities in all displayed advisories ("Combined First Fixed"). Please visit the Cisco IOS Software Checker or simply enter a Cisco IOS Software release in the following field to determine whether it is affected by any of the advisories in this bundled publication.

  (Example entry: 15.1(4)M2)

  Cisco IOS XE Software

  Cisco IOS XE Software is affected by the vulnerability described in this advisory.
  
  
  

  Cisco IOS XE Software Release	First Fixed Release	First Fixed Release for All Advisories in the September 2014 Cisco IOS Software Security Advisory Bundled Publication
  2.1.x	Not vulnerable	Vulnerable; migrate to 3.7.6S or later.
  2.2.x	Not vulnerable	Vulnerable; migrate to 3.7.6S or later.
  2.3.x	Not vulnerable	Vulnerable; migrate to 3.7.6S or later.
  2.4.x	Not vulnerable	Vulnerable; migrate to 3.7.6S or later.
  2.5.x	Not vulnerable	Vulnerable; migrate to 3.7.6S or later.
  2.6.x	Not vulnerable	Vulnerable; migrate to 3.7.6S or later.
  3.1.xS	Vulnerable; migrate to 3.7.6S or later.	Vulnerable; migrate to 3.7.6S or later.
  3.1.xSG	Not vulnerable	Not vulnerable
  3.2.xS	Vulnerable; migrate to 3.7.6S or later.	Vulnerable; migrate to 3.7.6S or later.
  3.2.xSE	Not vulnerable	Vulnerable; migrate to 3.3.2SE
  3.2.xSG	Not vulnerable	Not vulnerable
  3.2.xXO	Not vulnerable	Not vulnerable
  3.2.xSQ	Not vulnerable	Not vulnerable
  3.3.xS	Vulnerable; migrate to 3.7.6S or later.	Vulnerable; migrate to 3.7.6S or later.
  3.3.xSE	Not vulnerable	3.3.2SE
  3.3.xSG	Not vulnerable	Vulnerable; migrate to 3.4.4SG or later.
  3.3.xXO	Not vulnerable	3.3.1XO
  3.3.xSQ	Not vulnerable	Not vulnerable
  3.4.xS	Vulnerable; migrate to 3.7.6S or later.	Vulnerable; migrate to 3.7.6S or later.
  3.4.xSG	Not vulnerable	3.4.4SG
  3.4.xSQ	Not vulnerable	Not vulnerable
  3.5.xS	Vulnerable; migrate to 3.7.6S or later.	Vulnerable; migrate to 3.7.6S or later.
  3.5.xE	Not vulnerable	3.5.2E
  3.6.xS	Vulnerable; migrate to 3.7.6S or later.	Vulnerable; migrate to 3.7.6S or later.
  3.6.xE	Not vulnerable	Not vulnerable
  3.7.xS	3.7.6S	Vulnerable; migrate to 3.7.6S or later.
  3.7.xE	Not vulnerable	Not vulnerable
  3.8.xS	Vulnerable; migrate to 3.10.4S or later.	Vulnerable; migrate to 3.10.4S or later.
  3.9.xS	Vulnerable; migrate to 3.10.4S or later.	Vulnerable; migrate to 3.10.4S or later.
  3.10.xS	3.10.4S	3.10.4S
  3.11.xS	Vulnerable; migrate to 3.12S or later.	Vulnerable; migrate to 3.12S or later.
  3.12.xS	Not vulnerable	Not vulnerable
  3.13.xS	Not vulnerable	Not vulnerable

  
  
  For a mapping of Cisco IOS XE Software releases to Cisco IOS Software releases, refer to Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S Release Notes, and Cisco IOS XE 3SG Release Notes.

  Cisco IOS XR Software

  Cisco IOS XR Software is not affected by any of the vulnerabilities that are disclosed in the September 2014 Cisco IOS Software Security Advisory Bundled Publication.

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 internal security testing.

URL

• http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20140924-sip

Revision History

• Revision 1.0

  2014-September-24

  Initial public release.

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