Summary

• A vulnerability in the implementation of the Lua interpreter that is integrated in Cisco IOS XE Software could allow an authenticated, local attacker to execute arbitrary code with root privileges on the underlying Linux operating system (OS) of an affected device.

  The vulnerability is due to insufficient restrictions on Lua function calls within the context of user-supplied Lua scripts. An attacker with valid administrative credentials could exploit this vulnerability by submitting a malicious Lua script. When this file is processed, an exploitable buffer overflow condition could occur. A successful exploit could allow the attacker to execute arbitrary code with root privileges on the underlying Linux OS of the affected device.

  Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-lua-rce-7VeJX4f

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected the following Cisco routers if they were running a vulnerable release of Cisco IOS XE Software:

  • 4000 Series Integrated Services Routers
  • ASR 1000 Series Aggregation Services Routers
  • Cloud Services Router 1000V Series
  • Integrated Services Virtual Routers

  For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.

  Products Confirmed Not Vulnerable

  Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.

  Cisco has confirmed that this vulnerability does not affect the following Cisco products:

  • IOS Software
  • IOS XR Software
  • NX-OS Software

Details

• At the time of publication, this vulnerability had been identified in the Cisco Unified Border Element (SP Edition) feature of Cisco IOS XE Software. This feature allows administrators to define policies to control the VoIP signaling and media that pass through the device. Cisco Unified Border Element (SP Edition) offers the capability of defining enhanced policies by using the Lua programming language. These user-defined Lua scripts are executed within the scripting sandbox of the device.

  However, the local implementation of the Lua interpreter imposes insufficient restrictions on the allowed Lua function calls within the scripting sandbox of the affected device. An attacker who has valid administrative credentials can submit a malicious Lua script that, when executed, will escape the scripting sandbox and execute arbitrary code with root privileges on the underlying Linux OS of an affected device.

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

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

  Cisco IOS and IOS XE Software

  To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides the Cisco Software Checker to identify any Cisco Security Advisories that impact a specific software release and the earliest release that fixes the vulnerabilities described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities described in all the advisories identified (“Combined First Fixed”).

  Customers can use the Cisco Software Checker to search advisories in the following ways:

  • Choose the software and one or more releases
  • Upload a .txt file that includes a list of specific releases
  • Enter the output of the show version command

  After initiating a search, customers can customize the search to include all Cisco Security Advisories, a specific advisory, or all advisories in the most recent bundled publication.

  Customers can also use the following form to determine whether a release is affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE Software release-for example, 15.1(4)M2 or 3.13.8S:

  By default, the Cisco Software Checker includes results only for vulnerabilities that have a Critical or High Security Impact Rating (SIR). To include results for Medium SIR vulnerabilities, customers can use the Cisco Software Checker on Cisco.com and check the Medium check box in the drop-down list under Impact Rating when customizing a search.

  For a mapping of Cisco IOS XE Software releases to Cisco IOS Software releases, refer to the Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S Release Notes, or Cisco IOS XE 3SG Release Notes, depending on the Cisco IOS XE Software release.

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.

Source

• This vulnerability was found by Jean Bernard Beuque of Cisco during internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-lua-rce-7VeJX4f

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2020-SEP-24

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