CVE-2026-43924 FOSSBilling has an open redirect via administrator-configured redirect targets
Attackers with admin access can configure malicious redirect targets, causing users to be silently redirected to external phishing sites via cached 301 responses.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-43924?
CVE-2026-43924 is a medium-severity vulnerability in FOSSBilling, published on 3 Jun 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Official description
FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.0, the Redirect module does not validate the URL scheme of administrator-configured destination URLs before storing or issuing redirects. This allows arbitrary external URLs to be configured as redirect targets, creating an open redirect vulnerability exploitable for phishing attacks. Users following a legitimate FOSSBilling URL can be silently redirected to an attacker-controlled external site. The redirect is issued as a 301 (Moved Permanently) response, which browsers cache persistently, amplifying the impact. Exploitation requires administrator privileges to create or modify redirect entries, limiting practical attack scenarios to multi-admin environments or compromised admin accounts. Version 0.8.0 fixes the issue. Some workarounds are available. Restrict admin access to the Redirect module to trusted administrators only and/or audit existing redirect entries in the database (the `extension_meta` table with `extension = 'mod_redirect'`) for any unexpected or external target URLs.
Weakness: CWE-601
Which versions are affected by CVE-2026-43924?
How do I fix CVE-2026-43924?
No fix has been published for CVE-2026-43924 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-43924 being exploited?
There is no known exploitation of CVE-2026-43924 in the wild and no public exploit code.
Sources
Also known as GHSA-v8rf-g37v-vgpx.