Two Critical vBulletin Vulnerabilities Exposed: What You Need to Know (CVE-2025-48827 & CVE-2025-48828)

Copyright & Fact Checker

Introduction:

vBulletin, one of the most widely used platforms for building online forums, is once again in the spotlight — this time for two serious security vulnerabilities: CVE-2025-48827 and CVE-2025-48828. These flaws, uncovered by security expert Ryan Dewhurst, demonstrate how small oversights in updates and patches can lead to dangerous remote code execution (RCE) vulnerabilities. While bulletin boards may seem like relics of the past, they are still prevalent in many communities and enterprise environments. This breach should serve as a major wake-up call to administrators who have yet to implement critical security patches or who underestimate the nuances introduced with language updates like PHP 8.1.

What Happened (30-Line Digest):

In May 2025, researcher Ryan Dewhurst revealed an alarming exploit affecting vBulletin — a popular forum software written in PHP. This vulnerability, tracked as CVE-2025-48827 and CVE-2025-48828, stems from a subtle but critical shift in how PHP 8.1 handles the Reflection API. Historically, developers restricted API access using private and public method visibility. However, PHP 8.1 changed the game: the ReflectionMethod::setAccessible function now does nothing, allowing all methods, including private ones, to be invoked by default.

The result? Malicious actors can now remotely trigger internal functions that were never intended to be exposed — including methods with sensitive or privileged capabilities. vBulletin, like many other platforms, used Reflection in its API implementation. This oversight made the software extremely vulnerable if deployed in an environment using PHP 8.1 or later.

Even worse, although a patch was quietly released in April 2024, it lacked clarity — no CVEs, no technical explanation, just a vague note urging administrators to update. Many ignored it due to the absence of visible urgency. Now, exploit attempts are spiking. Between May 25 and May 28, attacks targeting the /ajax/api/ad/replaceAdTemplate endpoint surged dramatically. Malicious scans have been traced to IPs originating from Poland, the UK, and networks that appear to be under coordinated control, suggesting that this vulnerability is actively being weaponized by multiple threat actors.

The case highlights two critical issues: updating too early (PHP 8.1 adoption) can introduce silent but deadly vulnerabilities, while updating too late (vBulletin patch delays) leaves doors wide open. This unfortunate catch-22 is proving costly for administrators who assumed their systems were safe.

What Undercode Say: (40-Line Analysis)

This is a textbook example of how miscommunication between software vendors and language maintainers can cascade into global security threats. The introduction of PHP 8.1’s behavior change — effectively nullifying method access restrictions via Reflection — should have sounded alarm bells for developers building or maintaining APIs. Yet, without proactive warnings, even experienced engineers were blindsided.

The affected vBulletin systems rely heavily on Reflection to expose safe API calls. But the platform never accounted for PHP’s altered behavior, essentially allowing external users to poke around internal, supposedly “private” code. The real risk lies in how easy this exploit is to launch. With just a crafted URL and the right method name, attackers can force execution of sensitive functions.

The deeper issue isn’t just the bug — it’s the delivery of the patch. Despite being rolled out in April 2024, the patch was wrapped in silence. No advisory, no technical deep dive, and certainly no CVE numbers to alert threat intelligence systems. This silence led to complacency. Admins didn’t treat the update as critical, especially since it came with no immediate symptoms or exploit proof-of-concept. Now they’re paying the price.

More worrying is the fact that attacks began just two days after Dewhurst’s blog went live. This rapid weaponization shows how tuned attackers are to blog disclosures, even those without full technical details. Within days, at least four separate IP addresses were actively scanning for the affected API route. Two of these IPs display almost identical behavior, indicating likely control by the same actor or group. The spread of exploit attempts over several days, combined with the origin diversity, also suggests that this vulnerability has entered automated toolkits.

What makes this even more dangerous is that forum platforms like vBulletin are often deployed by small-to-medium communities with limited IT support. These users are the least likely to notice a silent patch advisory or understand the risk introduced by new PHP versions. They’re the perfect targets.

Admins must now weigh two difficult truths: staying on old versions of PHP may keep certain security models intact, but exposes them to unrelated vulnerabilities. Jumping to newer PHP versions may silently break assumptions their applications were built on. Without clear communication and detailed changelogs from both PHP maintainers and application vendors like vBulletin, the ecosystem remains fragile.

This breach teaches a vital lesson about software maintenance: updating isn’t just about grabbing the latest version. It’s about understanding what’s changed, what’s removed, and how those shifts affect your architecture. Reflection used to be a safety net — in PHP 8.1, it’s a trap door.

Fact Checker Results: ✅🕵️‍♂️🔍

✅ Vulnerabilities CVE-2025-48827 and CVE-2025-48828 are real and linked to PHP 8.1’s change in method accessibility.
✅ Exploitation has been confirmed, with targeted API routes and scanning IPs documented.
✅ Patch was indeed released in April 2024 but lacked clear disclosure, increasing risk of unpatched systems.

Prediction: 🚨 What’s Coming Next?

Expect a rise in automated exploits targeting forums still using unpatched versions of vBulletin with PHP 8.1+. Security researchers may release proof-of-concept code, accelerating attacks. vBulletin may be forced to rework its API architecture to align with the new PHP behavior. In the meantime, many forums will remain vulnerable due to admin inaction or lack of awareness. Hosting providers could begin blacklisting affected endpoints to limit damage.

Now is the time to audit your forums, apply patches, and re-evaluate API exposure strategies — because the scanners are already knocking.