---
id: "CVE-2026-61511"
kind: "vulnerability"
aliases: ["CVE-2026-61511"]
title: "vBulletin: eval injection lets unauthenticated requests run server code"
severity: "critical"
cvss: 9.8
epss: 0.05607
exploited: false
status: "open"
category: "vendor"
products: []
ecosystems: []
tags: ["cloudflare", "forums", "lab-disclosure", "php", "self-hosted", "vbulletin", "vendor"]
not_affected_if: ["non-vbulletin-versions"]
published_at: "2026-07-27T14:16:59+00:00"
first_seen_at: "2026-10-24T17:33:06+00:00"
updated_at: "2026-10-25T12:38:49+00:00"
sources: [{"source": "lab", "url": "https://developers.cloudflare.com/changelog/post/2026-08-11-waf-release/", "first_seen_at": "2026-10-24T17:33:06+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-61511", "first_seen_at": "2026-10-24T18:53:56+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-61511", "first_seen_at": "2026-10-25T12:38:49+00:00"}]
---

# vBulletin: eval injection lets unauthenticated requests run server code

vBulletin 5.x through 5.7.5 and 6.x through 6.2.1 contain an eval injection flaw tracked as CVE-2026-61511, rated CVSS 9.8. Per Cloudflare's WAF changelog, successful exploitation may lead to remote code execution, with possible data exposure and service disruption.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed vBulletin version against the affected ranges (5.x through 5.7.5, 6.x through 6.2.1) in the admin control panel or the installed files; the sources do not name a file or command.
- Confirm whether Cloudflare's Managed Ruleset rule "vBulletin - Remote Code Execution - CVE:CVE-2026-61511" is in Block mode if traffic passes through Cloudflare.

## Fix

- Update vBulletin to a version outside the affected ranges; the first fixed version is unknown from these sources.
- Apply the vendor's recommended mitigations; the sources do not specify them.
- Until patched, keep the Cloudflare WAF rule "vBulletin - Remote Code Execution - CVE:CVE-2026-61511" in Block mode.

## Timeline

- 2026-10-24T17:33:06+00:00 lab https://developers.cloudflare.com/changelog/post/2026-08-11-waf-release/ — Cloudflare: WAF Release - 2026-08-11 · Changelog
- 2026-10-24T18:53:56+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-61511
- 2026-10-25T12:38:49+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-61511

## Documents

- [advisory] Cloudflare: WAF Release - 2026-08-11 · Changelog https://developers.cloudflare.com/changelog/post/2026-08-11-waf-release/

## From the sources

WAF Release - 2026-08-11 · Changelog

# Changelog

New updates and improvements at Cloudflare.

August 11, 2026

## WAF Release - 2026-08-11

This release introduces new protection for a remote code execution vulnerability in vBulletin and improves two existing detections.

Key Findings

- A new detection provides protection against vBulletin CVE-2026-61511.
- Two existing detections have been improved to strengthen coverage.

Impact

Successful exploitation of CVE-2026-61511 may lead to remote code execution on affected vBulletin systems, potentially resulting in unauthorized access, data exposure, service disruption, and broader compromise of the hosting environment. Administrators are strongly encouraged to apply vendor updates and recommended mitigations.

| Ruleset | Rule ID | Legacy Rule ID | Description | Previous Action | New Action | Comments |
| --- | --- | --- | --- | --- | --- | --- |
| Cloudflare Managed Ruleset | ...94f3006b | N/A | vBulletin - Remote Code Execution - CVE:CVE-2026-61511 | Log | Block | This is a new detection. |
| Cloudflare Managed Ruleset | ...098b749e | N/A | Version Control - Information Disclosure - Beta | Log | Block | This rule is merged into the original rule "Version Control - Information Disclosure" (ID: ...0550c529) |
| Cloudflare Managed Ruleset | ...d56225d8 | N/A | vBulletin - Code Injection - Invalid image format - CVE:CVE-2019-17132 - Beta | Log | Block | This rule is merged into the original rule "vBulletin - Code Injection - Invalid image format - CVE:CVE-2019-17132" (ID: ...8fe9f1c7) |

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_