XenForo <= 2.2.15 (Template System) Remote Code Execution Vulnerability
• Software Link:
• Affected Versions:
Version 2.2.15 and prior versions.
• Vulnerability Description:
XenForo implements a template system which gives complete control over the layout of XenForo pages. Through these templates, it might be possible to call certain “callback methods”, however there is a sort of “sandbox” which allows to solely call read-only methods: a method is to be considered read-only when it begins with one of the allowed prefixes, such as “get” or “filter”. Malicious users might be able to bypass this “sandbox” by abusing the getRepository() method from the XF\Mvc\Entity\Manager class in order to get an instance object of the XF\Util\Arr class, and from there they can abuse its filterRecursive() static method in order to execute arbitrary callbacks or functions (internally, this method calls the array_filter() PHP function with an attacker-controlled “callback” parameter). As such, this can be exploited to e.g. execute arbitrary OS commands by using a payload like the following within a template, which will try to execute the passthru() PHP function passing to it the string “whoami” as argument, potentially resulting in the execution of the “whoami” command on the web server:
{{ $xf.app.em.getRepository('XF\Util\Arr').filterRecursive(['whoami'],'passthru') }}
Successful exploitation of this vulnerability requires an account with permissions to administer styles or widgets.
• Solution:
Update to a fixed version or apply the vendor patches.
• Disclosure Timeline:
[22/02/2024] – Vulnerability details sent to SSD Secure Disclosure
[05/06/2024] – Vendor released patches and fixed versions
[14/06/2024] – CVE identifier requested
[16/06/2024] – CVE identifier assigned
[16/07/2024] – Coordinated public disclosure
• CVE Reference:
The Common Vulnerabilities and Exposures project (cve.mitre.org) has assigned the name CVE-2024-38458 to this vulnerability.
• Credits:
Vulnerability discovered by Egidio Romano.
• Other References:
https://xenforo.com/community/threads/222133
https://ssd-disclosure.com/ssd-advisory-xenforo-rce-via-csrf/