Summary

• A vulnerability in the TrustZone implementation in certain Broadcom MediaxChange firmware was reported by security researchers. To exploit this vulnerability on the affected Cisco products, the attacker would need to dismount the backplate of the device and trigger a specific series of impulses on the chipset. This would reload the device in a special mode allowing access to the bootshell. The attacker would then issue specific commands with crafted parameters in the bootshell, which would trigger the vulnerability. Exploitation of this vulnerability could result in arbitrary code execution with privilege escalation.

  At the time of publication, a link to the details about this vulnerability was not available.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-brcm-mxc-jul2021-26LqUZUh

Affected Products

• Cisco investigated its product line to determine which products may be affected by this vulnerability.

  The Vulnerable Products section of this advisory includes Cisco bug IDs for each affected product. The bugs are accessible through the Cisco Bug Search Tool and contain additional platform-specific information, including workarounds (if available) and fixed software releases.

  Any product or service not listed in the Vulnerable Products section of this advisory is to be considered not vulnerable.

  Vulnerable Products

  The following table lists Cisco products that are affected by the vulnerability that is described in this advisory. If a future release date is indicated for software, the date provided represents an estimate based on all information known to Cisco as of the Last Updated date at the top of the advisory. Availability dates are subject to change based on a number of factors, including satisfactory testing results and delivery of other priority features and fixes. If no version or date is listed for an affected component (indicated by a blank field and/or an advisory designation of Interim), Cisco is continuing to evaluate the fix and will update the advisory as additional information becomes available. After the advisory is marked Final, customers should refer to the associated Cisco bug(s) for further details. Unless otherwise documented, all software releases earlier than the first fixed release are to be considered affected by this vulnerability.

  Product	Cisco Bug ID	Fixed Release Availability
  Cisco IP Phone 8800 Series with Multiplatform Firmware Cisco IP Phone 8811 with Multiplatform Firmware Cisco IP Phone 8841 with Multiplatform Firmware Cisco IP Phone 8851 with Multiplatform Firmware Cisco IP Phone 8861 with Multiplatform Firmware	CSCvx08743	11.3(4) (available)
  Cisco IP Phone 8845 with Multiplatform Firmware Cisco IP Phone 8865 with Multiplatform Firmware	CSCvx08744	11.3(4) (available)
  Cisco IP Phone 8845 Cisco IP Phone 8865	CSCvx08753	14.0(1) (available)
  Cisco IP Phone 8800 Series Cisco IP Phone 8811 Cisco IP Phone 8841 Cisco IP Phone 8851 Cisco IP Phone 8861	CSCvx08762	14.0(1) (available)
  Cisco Wireless IP Phone 8821	CSCvx08807	11.0(6)SR1 (available)

  
  

  Products Confirmed Not Vulnerable

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

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• For information about fixed software releases, consult the Cisco bugs identified in the Vulnerable Products section of this advisory.

  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.

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

• Cisco would like to thank Yuanzhe Wu, James E. Posen, and Ang Cui of Red Balloon Security, Inc. for reporting this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-brcm-mxc-jul2021-26LqUZUh

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2021-JUL-07

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