vBulletin: Unauthenticated access to protected API controllers in vBulletin (CVE-2025-48827) #shorts

Summary

In this episode, we cover CVE-2025-48827, a critical vulnerability in vBulletin versions 5.0.0 through 5.7.5 and 6.0.0 through 6.0.3. The flaw allows unauthenticated attackers to bypass access controls on protected API controllers when vBulletin is running on PHP 8.1 or later. Active exploitation in the wild was observed in May 2025, leading to unauthorized access to forum backends.

Product details

vBulletin is a widely used forum and community software platform, powering thousands of discussion boards worldwide. The affected releases include vBulletin 5.0.0 up to 5.7.5 and vBulletin 6.0.0 up to 6.0.3. The software is written in PHP and often runs on LAMP stacks. Administrators rely on regular patching to keep their installations secure.

Vulnerability type summary

CVE-2025-48827 is classified under CWE-424: Improper Protection of Alternate Path. In this scenario, vBulletin’s API endpoint mishandles the method parameter, exposing protected functions to unauthenticated requests. The vulnerability exploits PHP’s handling of alternate code paths in API dispatch routines.

Details of the vulnerability

Researchers Egidio Romano and Ryan Dewhurst independently disclosed this flaw, emphasizing shortcomings in vBulletin’s patch management. Attackers craft requests to /api.php?method=protectedMethod, bypassing authentication checks on PHP 8.1+. Shortly after disclosure, threat actors combined this flaw with CVE-2025-48828 to gain unauthorized access, modify forum data, and potentially deploy further payloads. The exploit was spotted in the wild in May 2025, targeting unpatched vBulletin installations.

Conclusion

If you run vBulletin 5.0.0–5.7.5 or 6.0.0–6.0.3 on PHP 8.1+, apply the vendor’s patches immediately or upgrade to a non-affected version. Review your logs for unusual API calls, rotate credentials, and ensure your patch management processes are robust. Staying current on security updates and advisories is vital to prevent these bypass attacks.

Watch the full video on YouTube: CVE-2025-48827

Remediation and exploitation details

This chain involves the following actors

  • Unauthenticated Attacker: Invokes protected API methods without prior login or session

This following systems are involved

  • vBulletin Forum (Hosts community discussions): Runs vulnerable versions of the API on PHP 8.1 or later

Attack entry point

  • /api.php?method Parameter: HTTP parameter controlling which API controller method is invoked

Remediation actions

Forum Administrator
Apply the vendor’s security patches
vBulletin Forum
Forum Administrator
Upgrade software to versions beyond 5.7.5 or 6.0.3
vBulletin Forum
Forum Administrator
Enforce authentication checks on all API controllers
vBulletin Forum
Forum Administrator
Limit access to /api.php via web server or firewall rules
vBulletin Forum

Exploitation actions

Send an HTTP request to /api.php without credentials to confirm reachability

Unauthenticated Attacker
Probe the API endpoint
vBulletin Forum
Examples:
  • GET /api.php

Issue GET requests with guessed method names to enumerate unprotected controllers

Unauthenticated Attacker
Discover available API methods
vBulletin Forum
Examples:
  • GET /api.php?method=listSupportedMethods

Craft an HTTP GET including a known protected method in the method parameter

Unauthenticated Attacker
Invoke a protected method
vBulletin Forum
Examples:
  • GET /api.php?method=user.getUser&userId=1

Parse JSON responses to harvest user details or trigger write operations

Unauthenticated Attacker
Extract data or perform actions
vBulletin Forum
Examples:
  • GET /api.php?method=content.deleteThread&threadId=123

Use a script or tool to loop through a list of installations and call protected methods

Unauthenticated Attacker
Automate against multiple targets
vBulletin Forum
Examples:
  • bash exploit.sh targets.txt

Related Content

NOTE: The following related content has not been vetted and may be unsafe.

CVE database technical details

CVE ID
CVE-2025-48827
Description
vBulletin 5.0.0 through 5.7.5 and 6.0.0 through 6.0.3 allows unauthenticated users to invoke protected API controllers' methods when running on PHP 8.1 or later, as demonstrated by the /api.php?method=protectedMethod pattern, as exploited in the wild in May 2025.
Provider
mitre
CWE / problem types
CWE-424 Improper Protection of Alternate Path
Affected Software Versions
vBulletin:vBulletin:[{'lessThanOrEqual': '5.7.5', 'status': 'affected', 'version': '5.0.0', 'versionType': 'custom'}, {'lessThanOrEqual': '6.0.3', 'status': 'affected', 'version': '6.0.0', 'versionType': 'custom'}]
Date Published
2025-05-27T00:00:00.000Z
Last Updated
2025-05-27T18:03:31.961Z