# CVE-2026-61511: vBulletin - RCE

> Live exploitation tracking for CVE-2026-61511 by the CrowdSec Live Exploit Tracker, built from real-world attack data crowdsourced from CrowdSec's global network.

Page: https://tracker.crowdsec.net/cves/CVE-2026-61511

## Key facts

- **Exploitation phase:** Limited Exploitation. The vulnerability is known but shows very limited attacker interest or exploitation activity.
- **CVSS score:** 9.3
- **Public exploit available:** Yes
- **Affected products:** vBulletin
- **Weaknesses:** CWE-95 (Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection'))
- **Tags:** forum, php

## Description

vBulletin 5.x through 5.7.5 and 6.x through 6.2.1 contains an eval injection vulnerability in the vB5_Template_Runtime::runMaths() method within the template runtime that allows unauthenticated remote attackers to execute arbitrary PHP code by supplying crafted input through the pagenav[pagenumber] parameter. Attackers can exploit the insufficiently restrictive regex filter by using phpfuck-style encoding with permitted characters to inject and execute arbitrary PHP code via the unauthenticated ajax/render template route without any authentication.

## CrowdSec analysis

[CVE-2026-61511](https://euvd.enisa.europa.eu/vulnerability/CVE-2026-61511) is a critical eval injection vulnerability in vBulletin that allows unauthenticated remote attackers to execute arbitrary PHP code through the unauthenticated template-rendering route. Exploitation involves crafted input in the `pagenav[pagenumber]` parameter to bypass filtering and compromise the confidentiality, integrity, and availability of the affected server.

CrowdSec has been tracking this vulnerability and its exploits since 28th of July 2026.

CrowdSec network observations suggest that most exploitation of CVE-2026-61511 involves focused reconnaissance to identify viable targets. Attackers typically tailor their campaigns based on system exposure and configuration. It is unlikely that a given attack is accidental.
Additionally, according to week-over-week analysis by CrowdSec, exploitation of CVE-2026-61511 is surging. Attack volumes are spiking well above historical norms, indicating widespread and escalating interest from threat actors. CVE-2026-61511 is currently experiencing high visibility and active exploitation across the internet.

Attackers target various endpoints with a URL-encoded POST parameter `routestring=ajax%2Frender%2Fpagenav` and a crafted `pagenav[pagenumber]` expression designed to trigger eval injection in vBulletin’s template runtime. Detection should focus on requests containing the `ajax/render/pagenav` route and deeply nested arithmetic, concatenation, or exponentiation syntax in the `pagenav[pagenumber]` parameter.

## Timeline

- 2026-07-27: CVE Published. CVE-2026-61511 is published to NVD.
- 2026-07-28: Rule Released. CrowdSec releases a rule to detect CVE-2026-61511 exploitation attempts against the CrowdSec Network.
- 2026-07-28: CrowdSec First Seen. CrowdSec observes in-the-wild exploitation of CVE-2026-61511 for the first time.

## References

- https://www.vulncheck.com/advisories/vbulletin-eval-injection-rce-via-vb5-template-runtime-php
- https://karmainsecurity.com/KIS-2026-13
- https://github.com/alex700/nuclei-templates/blob/c142a111bd422b37217e516a822fba6d8cd80c68/http/cves/2026/CVE-2026-61511.yaml

## Live exploitation data

The [Live Exploit Tracker page](https://tracker.crowdsec.net/cves/CVE-2026-61511) follows observed exploitation activity for CVE-2026-61511. [Request an API key](https://tracker.crowdsec.net/request-api-key) for full access to its exploitation timeline, attacking IP addresses and blocklists.