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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

Overview

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.

Description

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.

Impact

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.

Solution

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 https://dl.duosecurity.com/duo-win-login-latest.exe

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
CVSSv2 Vector: (AV:L/AC:H/Au:M/C:C/I:C/A:N/E:ND/RL:OF/RC:C/CDP:ND/TD:ND/CR:H/IR:H/AR:ND)

References

Timeline

2014-03-21

  • Duo discovers issue internally, identifies and implements fix

2014-04-01

  • Release is posted on dl.duosecurity.com

2014-04-03

  • Advisory is drafted, Duo performs additional testing

2014-05-12

  • Advisory is shared with affected Enterprise customers

2014-05-20

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

2014-05-27

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

Credits/Contact

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