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Duo Product Security Advisory

Advisory ID: DUO-PSA-2014-005
Publication Date: 2014-05-12
Revision Date: 2014-05-27
Status: Confirmed, Fixed
Document Revision: 3


Duo Security has identified an issue in its Credential-Provider based Remote Desktop Protocol (RDP) integrations (e.g. those installed on Windows versions from Vista / Server 2008) which may allow a user with an expired password to - upon completing primary and secondary authentication - switch to another user account using that account's primary credentials, skipping secondary authentication for that account.


The RDP integration works to add two-factor authentication to Windows logins, both Remote Desktop and (optionally) the local console. When a user has provided valid credentials (username and password), the integration presents a second-factor authentication dialog for the provided username. Under normal operation, when the second-factor authentication is successful, the user is logged on.

However, if the user's password has expired, then rather than logging the user in, the system will instead present a prompt requesting a password change. At this prompt, the user may type in a new (different) username and corresponding password - and if these credentials are valid, the user can proceed to log in with (and reset the password for) the new username without any corresponding second-factor authentication challenge for the new username.


A valid user (with a valid username/password and secondary authenticator) may, if his/her password expires, be able to login to another user account using only that account's username/password - i.e. without secondary authentication - after completing primary and secondary authentication for his/her own account.

Affected Product(s)

  • Duo RDP Integration (Credential-Provider based) versions 1.0.7 through 1.1.4, running on Windows Vista, Server 2008, and newer.


Install the latest version of the Duo Security RDP Integration (currently, version 1.1.7) on your host. The latest version can be downloaded at

Vulnerability Metrics

Vulnerability Class: Privilege Context Switching Error (CWE-270)
Remotely Exploitable: No
Authentication Required: Yes
Severity: Medium
CVSSv2 Overall Score: 5.1
CVSSv2 Group Scores: Base: 5.3, Temporal: 4.6, Environmental: 5.1




  • Duo discovers issue internally, identifies and implements fix


  • Release is posted on


  • Advisory is drafted, Duo performs additional testing


  • Advisory is shared with affected Enterprise customers


  • Advisory is shared with affected Business customers
  • Version number incremented to reflect timeline update


  • Advisory is shared with affected Personal and Trial customers
  • Version number incremented to reflect timeline update


Feedback regarding this issue should be sent to and reference "DUO-PSA-2014-005" in the subject.