What is CVE-2011-10018?

CVE-2011-10018 is a critical-severity vulnerability in Mybb, classified under Code Injection. CVSS score: 9.8/10. Published 2025-08-13.

How severe is CVE-2011-10018?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2011-10018 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

RCE in Mybb

CVE-2011-10018

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.

Vulnerability class: RCE (Remote Code Execution)

Published 2025-08-13 · last modified 2026-06-16.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.020 (79.7th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 80th percentile — 79.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.020 · newest: 0.020 · change: 0.000

Affected products

Mybb — versions 1.6.4
Mybb Group Forum Software — versions 1.6.4

Weakness classification (CWE)

Public proof-of-concept exploits

rapid7/metasploit-framework

References

raw.githubusercontent.com/rapid7/metasploit-framework/master/modules/exploits/u… (Product, exploit)
www.exploit-db.com/exploits/17949 (Exploit, exploit)
web.archive.org/web/20111015224948/http://secunia.com/advisories/46300/ (Third Party Advisory, third-party-advisory)
blog.mybb.com/2011/10/06/1-6-4-security-vulnerabilit/ (vendor-advisory, patch, Vendor Advisory)
www.vulncheck.com/advisories/mybb-backdoor-arbitrary-command-execution (Third Party Advisory, third-party-advisory)

Frequently asked questions

What is CVE-2011-10018?: CVE-2011-10018 is a critical-severity vulnerability in Mybb, classified under Code Injection. CVSS score: 9.8/10. Published 2025-08-13.
How severe is CVE-2011-10018?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2011-10018 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.