Critical Unauthenticated API Access in vBulletin
Severity: Critical (CVSS 10.0)
Published: May 27, 2025
Summary
A critical vulnerability in vBulletin versions 5.0.0 through 5.7.5 and 6.0.0 through 6.0.3 allows unauthenticated users to invoke protected API controller methods when running on PHP 8.1 or later. This flaw, identified as CVE-2025-48827, enables attackers to bypass authentication mechanisms by directly accessing API endpoints, such as /api.php?method=protectedMethod. The vulnerability has been exploited in the wild as of May 2025.
Affected Versions
- vBulletin 5.0.0 – 5.7.5
- vBulletin 6.0.0 – 6.0.3
- Only when running on PHP 8.1 or later
Technical Details
The vulnerability arises from improper protection of alternate paths (CWE-424), where the application fails to adequately restrict access to certain API methods. Specifically, when vBulletin is deployed on PHP 8.1 or newer, certain protected API controller methods become accessible without proper authentication checks. This allows remote attackers to execute actions that should be restricted, potentially leading to full system compromise.
Recommended Mitigation
- Upgrade vBulletin: Apply the latest patches provided by vBulletin to address this vulnerability.
- Restrict Access: Implement firewall rules or other network controls to limit access to the
/api.phpendpoint. - Monitor Logs: Review server logs for any unusual or unauthorized access patterns to API endpoints.
- PHP Version Consideration: If immediate patching is not feasible, consider downgrading to a PHP version prior to 8.1 as a temporary mitigation, understanding this may have other implications.
Affected Environments
- Web applications utilizing vBulletin versions 5.0.0 through 5.7.5 or 6.0.0 through 6.0.3 on PHP 8.1 or later.
- Forums or communities with publicly accessible
/api.phpendpoints.
FOFA Exposure Example – vBulletin API Endpoints
Search for potentially exposed vBulletin API endpoints vulnerable to CVE-2025-48827:
-
body="/api.php?method=" && server="vBulletin"
Finds vBulletin API endpoints that may expose unauthenticated methods, especially dangerous on PHP 8.1+.
TTP Mapping (MITRE ATT&CK)
- T1190 – Exploit Public-Facing Application
- T1059 – Command and Scripting Interpreter
- T1210 – Exploitation of Remote Services
