CVE-2023-40033: Server-Side Request Forgery via Avatar upload in flarum
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 allowurlfopen which will prevent the fetching of external files via URLs.
Credits Adam Kues - Assetnote
Other sources
Flarum is an open source forum software. Flarum is affected by a vulnerability that allows an attacker to conduct a Blind Server-Side Request Forgery (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. This has been patched in Flarum version 1.8.0. Users are advised to upgrade. Users unable to upgrade may disable PHP's allowurlfopen which will prevent the fetching of external files via URLs as a temporary workaround for the SSRF aspect of the vulnerability.
— MITRE
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2023-40033?
CVE-2023-40033 is rated as a critical severity vulnerability due to its potential for Blind SSRF attacks and server file disclosure.
How do I fix CVE-2023-40033?
To fix CVE-2023-40033, upgrade Flarum to version 1.8.0 or later.
What type of attack does CVE-2023-40033 allow?
CVE-2023-40033 allows attackers to perform Blind SSRF attacks or disclose sensitive files on the server.
Who is affected by CVE-2023-40033?
All users running versions of Flarum below 1.8.0 are vulnerable to CVE-2023-40033.
Can CVE-2023-40033 be exploited by basic user accounts?
Yes, attackers can exploit CVE-2023-40033 using basic user accounts on any vulnerable Flarum forum.