Summary

• A vulnerability in the T1/E1 driver queue implementation of Cisco IOS Software could allow an unauthenticated, remote attacker to cause an interface wedge condition, which could lead to loss of connectivity, loss of routing protocol adjacency, and could result in a denial of service (DoS) scenario.
  
  The vulnerability is due to incorrect implementation of the T1/E1 driver queue. An attacker could exploit this vulnerability by sending bursty traffic through the affected interface driver. Repeated exploitation could cause a DoS condition.
  
  Workarounds to mitigate this vulnerability are available.
  
  Cisco has released software updates that address this vulnerability. This advisory is available at the following link: 
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20130925-wedge
  

  Note: The September 25, 2013, Cisco IOS Software Security Advisory bundled publication includes eight Cisco Security Advisories. All advisories address vulnerabilities in Cisco IOS Software. Each Cisco IOS Software Security Advisory lists the Cisco IOS Software releases that correct the vulnerability or vulnerabilities detailed in the advisory as well as the Cisco IOS Software releases that correct all Cisco IOS Software vulnerabilities in the September 2013 bundled publication.

  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_sep13.html

  
  

Affected Products

• 
  

  Vulnerable Products

  Cisco devices running affected Cisco IOS Software versions configured with T1/E1 interface module signaling are vulnerable.
  A device is vulnerable if all the following criteria are met:
  

  
  

  • An interface controller configured for T1/E1 channel group is using the affected High-Level Data Link Control 32 (HDLC32) driver.
  • T1/E1 controller clock source is configured for line or internal

  
  Note: The affected HDLC32 driver is only used on VWIC2 interface cards for Cisco 1900, 2900 and 3900 Series Integrated Services Routers (ISR).
   
  To determine whether a Cisco IOS device is configured with T1/E1 signaling on a controller using HDLC32 driver, issue the show controllers command.  
  
  The following example shows a Cisco IOS device that is affected by this vulnerability. The device is vulnerable because the interface Serial0/0/0, configured for T1 signaling is using an HDLC32 driver as indicated by the “Hardware is HDLC32” output:

  
  

  Router#show controllers Serial0/0/0:0
  Interface Serial0/0/0:0
  Hardware is HDLC32
  < output truncated >
  
  

  Note: The vulnerability in the HDLC32 device driver on VWIC2 interface cards is not specific to Cisco High-Level Data Link Control network protocol encapsulation. Any supported encapsulation type on VWIC2 interface cards will result in the vulnerability.
  
  To determine a clock source type configured on a T1/E1 interface on a Cisco IOS device, issue the show controllers T1/E1 command. 
  The following example shows an E1 interface on a Cisco IOS device configured with line clock source:
  

  
  

  
  

  Router#show controllers e1 
  E1 0 is up. 
    Applique type is Channelized E1 - balanced 
  !--- output truncated
  Framing is CRC4, Line Code is HDB3, Clock Source is Line Primary. 
  !--- output truncated
  
  
  

  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 15.0(1)M1 with an installed image name of C3900-UNIVERSALK9-M:

  Router> show version 
  Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), Version 15.0(1)M1, RELEASE SOFTWARE (fc1)
  Technical Support: http://www.cisco.com/techsupport
  Copyright (c) 1986-2009 by Cisco Systems, Inc.
  Compiled Wed 02-Dec-09 17:17 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" at http://www.cisco.com/web/about/security/intelligence/ios-ref.html.

  
  

  Products Confirmed Not Vulnerable

  Cisco IOS XR software is not affected by the vulnerability disclosed in this advisory.
  

  
  Cisco IOS XE software is not affected by the vulnerability disclosed in this advisory.
  
  

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

  
  

Details

• A vulnerability in the T1/E1 driver queue implementation of Cisco IOS Software could allow an unauthenticated, remote attacker to cause an interface wedge condition, which could lead to loss of connectivity, loss of routing protocol adjacency, and could result in a denial of service (DoS) scenario.
  
  The vulnerability is due to incorrect implementation of the T1/E1 driver queue. An attacker could exploit this vulnerability by sending bursty traffic through the affected interface driver. Repeated exploitation could cause a DoS condition.
  
  A device is vulnerable if it is configured with T1/E1 signaling on an interface that is using an HDLC32 driver.
  
  An attacker with some knowledge of the affected infrastructure could exploit this vulnerability by sending a bursty profile of network packets through vulnerable devices. Successful exploitation of the vulnerability could allow an attacker to wedge the transmit queue of an egress interface.
  

  
  

  Workarounds to mitigate this vulnerability are available.
  
  Valid network traffic could trigger this vulnerability on devices that are considered vulnerable. An attacker could send an bursty profile of network packets egressing an interface with set conditions to exploit this vulnerability. Recovery from this interface queue wedge requires a reload of the device.
  
  An interface queue wedge is a class of vulnerability where certain packets are received and queued by a Cisco IOS router or switch but, due to a processing error, are never removed from the queue.
  
  For more information about queue wedges and a few detection mechanisms that may be used to identify a blocked interface on Cisco IOS Software (including a white paper describing how this condition can be detected using SNMP) see http://blogs.cisco.com/security/comments/cisco_ios_queue_wedges_explained/.
  
  This vulnerability has been documented in Cisco bug ID CSCub67465 (registered customers only) and has been assigned the Common Vulnerabilities and Exposures (CVE) ID CVE-2013-5477.
  

  
  

  
  

Workarounds

• If a hardware upgrade is an option, a possible workaround would be to use VWIC3-T1/E1 or HWIC-T1/E1 interface cards instead of the VWIC2 interface card.
  Alternatively, if the T1/E1 controller is configured for clock source line, and only a single channel-group is configured under controller, a possible workaround is to configure clock source line independent.

  
  

  The following identification mechanism exist for this vulnerability.

  
  

  Embedded Event Manager (EEM)

   

  A Cisco IOS Embedded Event Manager (EEM) policy that is based on Tool Command Language (Tcl) can be used on vulnerable Cisco IOS devices to identify and detect an interface queue wedge that is caused by this vulnerability. The policy allows administrators to monitor the interfaces for Cisco IOS devices and detect when the interface input queues are full. When Cisco IOS EEM detects potential exploitation of this vulnerability, the policy can trigger a response by sending an alert to the network administrator, who could then decide to implement an upgrade, implement suitable mitigations or reload the device to clear the input queue.
  
  The Tcl script is available for download at the "Cisco Beyond: Embedded Event Manager (EEM) Scripting Community" at the following link: https://supportforums.cisco.com/docs/DOC-19337
  
  The Cisco Security blog "Cisco IOS Queue Wedges Explained" can be viewed at the following link: http://blogs.cisco.com/security/cisco_ios_queue_wedges_explained/
  

  
  

  
  

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

  Each row of the following Cisco IOS Software table corresponds to a Cisco IOS Software train. If a particular train is vulnerable, the earliest releases that contain the fix are listed in the First Fixed Release column. The First Fixed Release for All Advisories in the September 2013 Bundled Publication column lists the earliest possible releases that correct all the published vulnerabilities in the Cisco IOS Software Security Advisory bundled publication. Cisco recommends upgrading to the latest available release where possible.

  The Cisco IOS Software Checker allows customers to search for Cisco Security Advisories that address specific Cisco IOS Software releases. This tool is available on the Cisco Security (SIO) portal at https://sec.cloudapps.cisco.com/security/center/selectIOSVersion.x

  Major Release	Availability of Repaired Releases
  Affected 12.0-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Cisco IOS Software Security Advisory Bundled Publication
  There are no affected 12.0 based releases
  Affected 12.2-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Cisco IOS Software Security Advisory Bundled Publication
  12.2EX	Not vulnerable	Vulnerable; First fixed in Release 15.0SE
  12.2EY	Not vulnerable	Vulnerable; First fixed in Release 15.2S
  12.2EZ	Not vulnerable	Releases prior to 12.2(60)EZ2 are vulnerable; Releases 12.2(60)EZ2 and later are not vulnerable. First fixed in Release 15.0SE
  12.2IRB	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2IRC	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2IRD	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2IRE	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2IRF	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2IRG	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2IRH	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2IRI	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2IXG	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2IXH	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2MC	Not vulnerable	Vulnerable; First fixed in Release 15.1M
  12.2MRA	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2MRB	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SB	Not vulnerable	12.2(33)SB15
  12.2SCA	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCB	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCC	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCD	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCE	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCF	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCG	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCH	Not vulnerable	12.2(33)SCH1
  12.2SE	Not vulnerable	12.2(55)SE8
  12.2SEG	Not vulnerable	Vulnerable; First fixed in Release 15.0SE
  12.2SG	Not vulnerable	12.2(53)SG10; available December 2013 *
  12.2SGA	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SM	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SQ	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SRA	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2SRB	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2SRC	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2SRD	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2SRE	Not vulnerable	12.2(33)SRE9
  12.2STE	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SV	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SVD	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SVE	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SW	Not vulnerable	Vulnerable; First fixed in Release 15.1M
  12.2SXF	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SXH	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SXI	Not vulnerable	12.2(33)SXI12
  12.2SXJ	Not vulnerable	12.2(33)SXJ6
  12.2SY	Not vulnerable	Vulnerable; First fixed in Release 15.0SY
  12.2WO	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2XNA	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XNB	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XNC	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XND	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XNE	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XNF	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XO	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2ZYA	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  Affected 12.3-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Cisco IOS Software Security Advisory Bundled Publication
  There are no affected 12.3 based releases
  Affected 12.4-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Cisco IOS Software Security Advisory Bundled Publication
  There are no affected 12.4 based releases
  Affected 15.0-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Cisco IOS Software Security Advisory Bundled Publication
  15.0EA	Not vulnerable	15.0(2)EA1
  15.0EB	Not vulnerable	Vulnerable; migrate to any release in 15.2E
  15.0EC	Not vulnerable	Vulnerable; migrate to any release in 15.2E
  15.0ED	Not vulnerable	Note: Releases prior to 15.0(2)ED1 are vulnerable; Releases 15.0(2)ED1 and later are not vulnerable.
  15.0EH	Not vulnerable	Not vulnerable
  15.0EJ	Not vulnerable	Not vulnerable
  15.0EX	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0EY	Not vulnerable	15.0(2)EY2
  15.0EZ	Not vulnerable	Only Release 15.0(2)EZ is vulnerable
  15.0M	Vulnerable; First fixed in Release 15.1M	Vulnerable; First fixed in Release 15.1M
  15.0MR	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.0S	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Vulnerable; First fixed in Release 15.1S Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0SE	Not vulnerable	15.0(2)SE4
  15.0SG	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory. Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0SQA	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0SQB	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0SY	Not vulnerable	15.0(1)SY5
  15.0XA	Vulnerable; First fixed in Release 15.1M	Vulnerable; First fixed in Release 15.1M
  15.0XO	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory. Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  Affected 15.1-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Cisco IOS Software Security Advisory Bundled Publication
  15.1EY	Not vulnerable	Vulnerable; First fixed in Release 15.2S
  15.1GC	Vulnerable; First fixed in Release 15.1M	Vulnerable; First fixed in Release 15.1M
  15.1M	15.1(4)M7	15.1(4)M7
  15.1MR	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.1MRA	Not vulnerable	15.1(3)MRA2
  15.1S	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.1(3)S6 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.1SG	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.1(2)SG1 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.1SNG	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.1SNH	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.1SNI	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.1SVD	Not vulnerable	Not vulnerable
  15.1SVE	Not vulnerable	Not vulnerable
  15.1SVF	Not vulnerable	Not vulnerable
  15.1SY	Not vulnerable	15.1(1)SY2; Available on 28-OCT-13  15.1(2)SY
  15.1T	Vulnerable; First fixed in Release 15.1M	Vulnerable; First fixed in Release 15.1M
  15.1XO	Not vulnerable	Not vulnerable
  Affected 15.2-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Cisco IOS Software Security Advisory Bundled Publication
  15.2E	Not vulnerable	Not vulnerable
  15.2GC	15.2(4)GC	Vulnerable; migrate to any release in 15.4T
  15.2JA	15.2(4)JA1	15.2(4)JA1
  15.2JAX	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.2JB	15.2(2)JB2	15.2(2)JB2
  15.2JN	Not vulnerable	Not vulnerable
  15.2M	15.2(4)M3	15.2(4)M4
  15.2S	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.2(4)S4  Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.2SA	Not vulnerable	15.2(2)SA
  15.2SNG	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.2SNH	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.2SNI	Not vulnerable	Vulnerable; First fixed in Release 15.3S
  15.2T	15.2(2)T4 15.2(3)T4	15.2(3)T4
  Affected 15.3-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Cisco IOS Software Security Advisory Bundled Publication
  15.3M	Not vulnerable	Not vulnerable
  15.3S	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.3(2)S2  15.3(3)S Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.3T	15.3(1)T2 15.3(2)T	15.3(1)T2  15.3(2)T1

  
  * Cisco Catalyst 4500 Series Switches with Cisco Catalyst 4500 Supervisor Engines 6-E or 6L-E can migrate to Cisco IOS Software Release 15.1SG.
  
  

   

  Cisco IOS XR Software

  Cisco IOS XR Software is not affected by any of the vulnerabilities that are disclosed in the September 2013 Cisco IOS Software Security Advisory Bundled Publication. 
  
  

  Cisco IOS XE Software

  Cisco IOS XE Software is not affected by the vulnerability disclosed in this advisory.
  
  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.
  
  

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 resolution of a support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20130925-wedge

Revision History

• Revision 1.0

  2013-September-25

  Initial public release

  Show Less