Summary

• Multiple vulnerabilities in the Link Layer Discovery Protocol (LLDP) subsystem of Cisco IOS Software, Cisco IOS XE Software, and Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition or execute arbitrary code with elevated privileges on an affected device. 

  For more information about these vulnerabilities, see the Details section of this advisory.

  Cisco has released software updates that address these vulnerabilities. There are no workarounds that address these vulnerabilities.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-lldp

  This advisory is part of the March 28, 2018, release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication, which includes 20 Cisco Security Advisories that describe 22 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: March 2018 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  These vulnerabilities affect Cisco devices that are running a vulnerable release of Cisco IOS Software, Cisco IOS XE Software, or Cisco IOS XR Software and are configured to use LLDP. The default state of the LLDP feature is platform- and release-dependent.

  For information about which Cisco IOS, IOS XE, and IOS XR Software releases are vulnerable, see the Fixed Software section of this advisory.

  Assessing the LLDP Configuration

  To determine whether a device is configured to use LLDP, administrators can log in to the device and use the show lldp command in the CLI. If the device is configured to use LLDP, the output of the command will be similar to the following:

  Router> show lldp
  
  Global LLDP Information:
     Status: ACTIVE
     LLDP advertisements are sent every 30 seconds
     LLDP hold time advertised is 120 seconds
     LLDP interface reinitialisation delay is 2 seconds

  If use of LLDP is configured for only specific interfaces of a device, administrators can instead use the show lldp interface command in the CLI to determine which interfaces are configured to use LLDP.

  Determining the Cisco IOS Software Release

  To determine which Cisco IOS Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and then refer to the system banner that appears. If the device is running Cisco IOS Software, the system banner displays text similar to Cisco Internetwork Operating System Software or Cisco IOS Software. The banner also displays the installed image name in parentheses, followed by the Cisco IOS Software release number and release name. Some Cisco devices do not support the show version command or may provide different output.

  The following example shows the output of the command for a device that is running Cisco IOS Software Release 15.5(2)T1 and has an installed image name of C2951-UNIVERSALK9-M:

  Router> show version
  
  Cisco IOS Software, C2951 Software (C2951-UNIVERSALK9-M), Version 15.5(2)T1, RELEASE SOFTWARE (fc1)
  Technical Support: http://www.cisco.com/techsupport
  Copyright (c) 1986-2015 by Cisco Systems, Inc.
  Compiled Mon 22-Jun-15 09:32 by prod_rel_team
  .
  .
  .

  For information about the naming and numbering conventions for Cisco IOS Software releases, see the Cisco IOS and NX-OS Software Reference Guide.

  Determining the Cisco IOS XE Software Release

  To determine which Cisco IOS XE Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and then refer to the system banner that appears. If the device is running Cisco IOS XE Software, the system banner displays Cisco IOS Software, Cisco IOS XE Software, or similar text.

  The following example shows the output of the command for a device that is running Cisco IOS XE Software Release 16.2.1 and has an installed image name of CAT3K_CAA-UNIVERSALK9-M:

  ios-xe-device# show version
  
  Cisco IOS Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version Denali 16.2.1, RELEASE SOFTWARE (fc1)
  Technical Support: http://www.cisco.com/techsupport
  Copyright (c) 1986-2016 by Cisco Systems, Inc.
  Compiled Sun 27-Mar-16 21:47 by mcpre
  .
  .
  .

  For information about the naming and numbering conventions for Cisco IOS XE Software releases, see the Cisco IOS and NX-OS Software Reference Guide.

  Determining the Cisco IOS XR Software Release

  To determine which Cisco IOS XR Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and then refer to the system banner that appears. If the device is running Cisco IOS XR Software, the system banner displays Cisco IOS XR Software or similar text. In addition, the System image file is field displays the location and name of the system image file that is running on the device, followed by the name of the hardware product.

  The following example shows the output of the show version command for a device that is running Cisco IOS XR Software Release 5.3.4:

  RP/0/RSP0/CPU0:ASR9001# show version
  Wed Jan 24 01:32:32.751 EST
  
  Cisco IOS XR Software, Version 5.3.4[Default]
  Copyright (c) 2017 by Cisco Systems, Inc.
  
  ROM: System Bootstrap, Version 2.04(20140227:092320) [ASR9K ROMMON],  
  
  ASR9001 uptime is 6 hours, 17 minutes
  System image file is "bootflash:disk0/asr9k-os-mbi-5.3.4.sp4-1.0.0/0x100000/mbiasr9k-rp.vm"
  
  cisco ASR9K Series (P4040) processor with 8388608K bytes of memory.
  P4040 processor at 1500MHz, Revision 2.0
  ASR-9001 Chassis
  .
  .
  .
  

  Products Confirmed Not Vulnerable

  No other Cisco products are currently known to be affected by these vulnerabilities.

  Cisco has confirmed that these vulnerabilities do not affect Cisco NX-OS Software.

Details

• Two vulnerabilities in the LLDP subsystem of Cisco IOS Software, Cisco IOS XE Software, and Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause a DoS condition or execute arbitrary code with elevated privileges.

  Details about the vulnerabilities are as follows.

  Link Layer Discovery Protocol Buffer Overflow Vulnerability

  A vulnerability in the LLDP subsystem of Cisco IOS Software, Cisco IOS XE Software, and Cisco IOS XR Software could allow an adjacent, unauthenticated attacker to cause a DoS condition or execute arbitrary code with elevated privileges.

  The vulnerability is due to improper error handling of malformed LLDP messages. An attacker who is connected directly to an interface of an affected device could exploit this vulnerability by submitting an LLDP protocol data unit (PDU) that is designed to trigger the issue. If successful, an exploitable buffer overflow condition may occur that could result in a DoS condition or the attacker gaining the ability to execute arbitrary code with elevated privileges.

  The Common Vulnerabilities and Exposures (CVE) ID for this vulnerability is: CVE-2018-0167

  The Security Impact Rating (SIR) for this vulnerability is: High

  The Cisco bug IDs for this vulnerability are: CSCvd73487 (Cisco IOS and IOS XE Software) and CSCuo17183 (Cisco IOS XR Software)

  Link Layer Discovery Protocol Format String Vulnerability

  A vulnerability in the LLDP subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an adjacent, unauthenticated attacker to cause a DoS condition or execute arbitrary code with elevated privileges.

  The vulnerability is due to improper handling of certain fields in an LLDP message. An attacker who is connected directly to an interface of an affected device could exploit this vulnerability by submitting an LLDP PDU that is designed to prime the device for exploitation. An attacker must then convince an authenticated user to execute a specific show command in the CLI of the affected device. If successful, the attacker could cause a DoS condition or gain the ability to execute arbitrary code with elevated privileges.

  The CVE ID for this vulnerability is: CVE-2018-0175

  The SIR for this vulnerability is: High

  The Cisco bug ID for this vulnerability is: CSCvd73664

Workarounds

• There are no workarounds that address these vulnerabilities.

Fixed Software

• Cisco has released free software updates that address the vulnerabilities described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license:
  https://www.cisco.com/c/en/us/products/end-user-license-agreement.html

  Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.

  When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, 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.

  Customers Without Service Contracts

  Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco TAC:
  https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html

  Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.

  Cisco IOS XR Software

  The following table lists major software release trains of Cisco IOS XR Software, indicates whether a release train is affected by the vulnerabilities described in this advisory and, if applicable, the first minor release that includes the fix for these vulnerabilities. Customers should migrate to an appropriate release as indicated in the following table:

  Software Train	First Fixed Release	Recommended Release
  4.1	No fix – migrate	Migrate to 5.3.4
  4.2	No fix – migrate	Migrate to 5.3.4
  4.3	No fix – migrate	Migrate to 5.3.4
  5.0	No fix – migrate	Migrate to 5.3.4
  5.1	5.1.3	5.1.3
  5.2	Not vulnerable	Not vulnerable
  5.3	Not vulnerable	Not vulnerable
  6.0	Not vulnerable	Not vulnerable
  6.1	Not vulnerable	Not vulnerable

Exploitation and Public Announcements

• In March 2022, the Cisco Product Security Incident Response Team (PSIRT) became aware of additional attempted exploitation of this vulnerability in the wild. Cisco continues to strongly recommend that customers upgrade to a fixed software release to remediate this vulnerability.

Source

• These vulnerabilities were found during the resolution of a Cisco TAC support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-lldp

Revision History

• Version	Description	Section	Status	Date
  1.2	Updated exploitation information.	Exploitation and Public Announcements	Final	2022-DEC-15
  1.1	Updated the metadata to indicate that multiple legacy Cisco IOS Software images are not vulnerable.	—	Final	2018-MAY-02
  1.0	Initial public release.	—	Final	2018-MAR-28

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