Summary

• A vulnerability in the smart card login authentication of Cisco Duo for macOS could allow an unauthenticated attacker with physical access to bypass authentication.

  This vulnerability exists because the assigned user of a smart card is not properly matched with the authenticating user. An attacker could exploit this vulnerability by configuring a smart card login to bypass Duo authentication. A successful exploit could allow the attacker to use any personal identity verification (PIV) smart card for authentication, even if the smart card is not assigned to the authenticating user.

  Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-duo-macOS-bypass-uKZNpXE6

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected Cisco Duo for macOS.

  For information about which Cisco software releases were vulnerable at the time of publication, see the Fixed Software section of this advisory. See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.

  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:

  • Duo for Windows
  • Duo for Linux

Workarounds

• There is a workaround that addresses this vulnerability.

  If customers prefer not to update Cisco Duo for macOS at this time, they can disable Should bypass 2FA when using smartcard on Cisco Duo for macOS on all devices. By requiring end users to authenticate using the Duo Prompt after logging in to a macOS device, customers will prevent unintended bypass of the Duo Prompt with an unverified smart card.

  To disable smart card 2FA bypass, run the following command in a terminal window:

  sudo plutil -replace smartcard_bypass -bool false /private/var/root/Library/Preferences/com.duosecurity.maclogon.plist

  While this workaround has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.

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.

  Fixed Releases

  At the time of publication, the release information in the following table(s) was accurate. See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.

  The left column lists Cisco software releases, and the right column indicates whether a release was affected by the vulnerability that is described in this advisory and which release included the fix for this vulnerability.

  Cisco Duo for macOS Authentication Software Release	First Fixed Release
  Earlier than 2.0	2.0.0

  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 internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-duo-macOS-bypass-uKZNpXE6

Revision History

• Version	Description	Section	Status	Date
  1.1	Added workaround.	Workarounds	Final	2022-SEP-29
  1.0	Initial public release.	-	Final	2022-SEP-28

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