Summary

• A vulnerability in the RADIUS feature of Cisco Identity Services Engine (ISE) could allow an unauthenticated, remote attacker to cause the affected system to stop processing RADIUS packets.

  This vulnerability is due to improper handling of certain RADIUS requests. An attacker could exploit this vulnerability by attempting to authenticate to a network or a service where the access server is using Cisco ISE as the RADIUS server. A successful exploit could allow the attacker to cause Cisco ISE to stop processing RADIUS requests, causing authentication/authorization timeouts, which would then result in legitimate requests being denied access.

  Note: To recover the ability to process RADIUS packets, a manual restart of the affected Policy Service Node (PSN) is required. See the Details section for more information.

  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-ise-dos-JLh9TxBp

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco ISE configured with RADIUS authentication services. RADIUS services are enabled by default. If Cisco ISE is being used for TACACS only, the device will not be affected.

  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.

Details

• To restore RADIUS processes on an affected node, a restart of that node is required.

  • In a one node deployment, the PSN persona will be located on that one node. That node will need to be restarted.
  • In a multi-node deployment, only the affected PSN node will need to be restarted.

  For more information on Cisco ISE personas, see the Cisco ISE Admin Guide.

  Note: If PSNs are behind a load balancer, the exploit traffic can cascade across to other PSNs.

  Note: If PSN node groups are configured, the exploit traffic will not cascade across to other PSNs.

  Restart Cisco ISE

  The procedure that follows is for stopping and then starting a Cisco ISE node from the CLI. During the restart period, any devices already authenticated will still be connected to the network. New authentications will not be processed unless PSN failover is configured.

  More details on each command can be found in the Cisco Identity Services Engine CLI Reference Guide.

  1. Log onto the affected PSN via the CLI.
  2. Issue the command application stop ise.
  3. Wait for the prompt to return.
  4. Issue the command application start ise.
  5. Wait for the prompt to return.
  6. Issue the command show application status ise to see the status of the processes. When the Application Server is running, authentications will take place and the node will be accessible via the GUI.

  PSN Failover Information

  • For PSN failover options, see the Policy Service Nodes and Node Groups section of this CiscoPress article.
  • For information on how to configure node groups, see the Policy Service Node section of the Cisco ISE Admin Guide.

Indicators of Compromise

• The indicator of compromise for this vulnerability is "RADIUS Authentication Failed" messages in the live logs where the failure reason is due to the EAP session limit being reached.

  Check Live Logs

  1. Log into the Cisco ISE Admin Node GUI.
  2. Navigate to the Operations page.
  3. Choose the RADIUS option.
  4. Then choose the Live Logs page.
  5. Find an "Authentication Failed" entry and click on the detailed report icon.

  If the Failure Reason shows "5443 RADIUS request dropped due to reaching EAP sessions limit," then this vulnerability has been potentially exploited.

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 with service contracts that entitle them to regular software updates should obtain security fixes through their usual update channels.

  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.

  The Cisco Support and Downloads page on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool.

  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

  In the following table(s), the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.

  Cisco ISE Software Release	First Fixed Release
  2.1 and earlier	Not vulnerable.
  2.2P16 and earlier	Not vulnerable.
  2.2P17 and later	Migrate to fixed release.
  2.3	Not vulnerable.
  2.4P11 and earlier	Not vulnerable.
  2.4P12 and later	Migrate to fixed release.
  2.6P4 and earlier	Not vulnerable.
  2.6P5 and later	2.6P111 (Target May 19, 2022)
  2.7P1 and earlier	Not vulnerable.
  2.7P2 and later	2.7P6
  3.0	3.0P5
  3.1	3.1P1

  1. Hotpatch on Cisco ISE 2.6P10 available upon request. Contact Cisco TAC to make the request.

  The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.

Exploitation and Public Announcements

• The Cisco 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-ise-dos-JLh9TxBp

Revision History

• Version	Description	Section	Status	Date
  1.1	Clarified fixed and vulnerable releases.	Fixed Software	Final	2022-MAR-03
  1.0	Initial public release.	-	Final	2022-MAR-02

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