REST endpoint user impersonation using authentication module functionality - CVE-2017-16858

The 'crowd-application' plugin module (notably used by the Google Apps plugin) in Atlassian Crowd from version 1.5.0 before version 3.1.2 allowed an attacker to impersonate a Crowd user in REST requests by being able to authenticate to a directory bound to an application using the feature. Given the following situation: the Crowd application is bound to directory 1 and has a user called admin and the Google Apps application is bound to directory 2, which also has a user called admin, it was possible to authenticate REST requests using the credentials of the user coming from directory 2 and impersonate the user from directory 1.

Affected versions:

• All versions of Crowd from 1.5.0 to 3.1.1

Fix

• Crowd 3.1.2 is available to download at https://www.atlassian.com/software/crowd/download

Risk mitigation

• This issue can be mitigated by ensuring that applications created by plugins using the 'crowd-application' plugin module (notably the google-apps application) have a consistent directory order with the Crowd application or that no such applications are defined in Crowd