Summary

• A vulnerability in the TCP packet processing functionality of Cisco IP Phones could allow an unauthenticated, remote attacker to cause the phone to stop responding to incoming calls, drop connected calls, or unexpectedly reload.

  The vulnerability is due to insufficient TCP ingress packet rate limiting. An attacker could exploit this vulnerability by sending a high and sustained rate of crafted TCP traffic to the targeted device. A successful exploit could allow the attacker to impact operations of the phone or cause the phone to reload, leading to a denial of service (DoS) condition.

  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-voip-phone-flood-dos-YnU9EXOv

Affected Products

• Vulnerable Products

  This vulnerability affects the following Cisco IP Phones if they are running a vulnerable firmware release:

  • IP DECT 210 Multi-Cell Base Station with Multiplatform Firmware
  • IP DECT 6825 with Multiplatform Firmware
  • IP Phone 8811 Series with Multiplatform Firmware
  • IP Phone 8841 Series with Multiplatform Firmware
  • IP Phone 8851 Series with Multiplatform Firmware
  • IP Phone 8861 Series with Multiplatform Firmware
  • Unified IP Conference Phone 8831 for Third-Party Call Control
  • Webex Room Phone

  Note: The default configurations of these devices are vulnerable.

  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:

  • ATA 190 Analog Telephone Adapter
  • ATA 191 Analog Telephone Adapter
  • IP Conference Phone 7832
  • IP Conference Phone 7832 with Multiplatform Firmware
  • IP Conference Phone 8832
  • IP Conference Phone 8832 with Multiplatform Firmware
  • IP Phone 6800 Series with Multiplatform Firmware
  • IP Phone 6821 with Multiplatform Firmware
  • IP Phone 7800 Series
  • IP Phone 7800 Series with Multiplatform Firmware
  • IP Phone 8800 Series
  • IP Phone 8845
  • IP Phone 8865
  • IP Phone 8865 with Multiplatform Firmware
  • SPA112 2-Port Phone Adapter
  • SPA122 Analog Telephone Adapter (ATA) with Router
  • SPA232D Multi-Line DECT Analog Telephone Adapter (ATA)
  • SPA525G 5-Line IP Phone
  • Unified IP Phone 3905
  • Unified IP Phone 6901
  • Unified IP Phone 6911
  • Unified IP Phone 7900 Series
  • Unified IP Conference Phone 8831
  • Wireless IP Phone 8821

  Note: The devices listed may see a performance impact from the same attack traffic, but will recover without user intervention once the attack traffic is stopped.

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• Cisco has released free software updates that address the vulnerability 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 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.

  Fixed Releases

  Customers are advised to upgrade to an appropriate fixed firmware release as indicated in the following table:

  Cisco IP Phone Model	Cisco Bug ID	First Fixed Release
  IP DECT 210 Multi-Cell Base Station with Multiplatform Firmware IP DECT 6825 with Multiplatform Firmware	CSCvt83239	4.8.1
  IP Phone 8811 Series with Multiplatform Firmware IP Phone 8841 Series with Multiplatform Firmware IP Phone 8851 Series with Multiplatform Firmware IP Phone 8861 Series with Multiplatform Firmware	CSCvs66815	11.3.2
  Unified IP Conference Phone 8831 for Third-Party Call Control	CSCvu36012	There is no fixed firmware available at this time.
  Webex Room Phone	CSCvu36026	1.2.0

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 during the resolution of a Cisco TAC support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-voip-phone-flood-dos-YnU9EXOv

Revision History

• Version	Description	Section	Status	Date
  1.2	Updated the Fixed Software section to indicate fix released for Webex Room Phone.	Fixed Software	Final	2021-JAN-19
  1.1	Updated the Fixed Software section for the Webex Room Phone.	Fixed Software	Final	2020-DEC-22
  1.0	Initial public release.	-	Final	2020-NOV-04

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