Flarum vulnerable to LFI and Blind SSRF via Avatar upload
Description
Impact
The Flarum forum software is affected by a vulnerability that allows an attacker to conduct a Blind SSRF attack or disclose any file on the server, even with a basic user account on any Flarum forum. By uploading a file containing a URL and spoofing the MIME type, an attacker can manipulate the application to execute unintended actions. The vulnerability is due to the behavior of the intervention/image package, which attempts to interpret the supplied file contents as a URL, which then fetches its contents. This allows an attacker to exploit the vulnerability to perform SSRF attacks, disclose local file contents, or conduct a blind oracle attack.
Patches
This has been patched in Flarum v1.8.
Workarounds
As a temporary workaround for the SSRF aspect of the vulnerability, one can disable PHP's allow_url_fopen which will prevent the fetching of external files via URLs.
Credits
Adam Kues - Assetnote