dbcve.org
MybbApplication

CVE-2011-5133

HIGH · 10.0 CVSS v2.0 Published 2012-08-30
Fix available
A fix is available. Upgrade to after 1.6.4 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Unspecified vulnerability in MyBB before 1.6.5 has unknown impact and attack vectors, related to an "unparsed user avatar in the buddy list."

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This is a stored Cross-Site Scripting (XSS) vulnerability in MyBB versions prior to 1.6.5 where user avatar URLs in the buddy list are not properly sanitized before being rendered. An attacker could embed malicious JavaScript code in their avatar URL, which would execute in the browsers of users viewing the buddy list, potentially leading to session hijacking or account compromise.

MitigationUpgrade MyBB to version 1.6.5 or later which includes proper sanitization of avatar data in the buddy list. If immediate upgrade is not possible, consider disabling the buddy list feature or implementing web application firewall rules to detect malicious avatar URL patterns.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
MybbApplication
Affected:<= 1.6.4= 1.1.0= 1.1.1= 1.1.2= 1.1.3= 1.1.4= 1.1.5= 1.1.6= 1.1.7= 1.1.8= 1.2= 1.2.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Authentication
None
Confidentiality
Complete
Integrity
Complete
Availability
Complete

AV:N/AC:L/Au:N/C:C/I:C/A:C

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed MyBB version
    Access the MyBB admin control panel and navigate to the version information page, or check the version.php file in the MyBB root directory.
    Affected if The installed version is 1.6.4 or lower, or any of these specific versions: 1.1.0 through 1.1.8, 1.2, or 1.2.0.
  2. Confirm buddy list feature is accessible
    Verify that the buddy list functionality is enabled and accessible to users on the forum. This can be checked in the admin control panel under user group permissions or forum settings.
    Affected if The buddy list feature is enabled and users can view other users' buddy lists.
  3. Verify avatar display in buddy list
    Check if the forum allows users to set custom avatar URLs and that these avatars are displayed when viewing a user's buddy list. This is typically found in user profile or avatar settings.
    Affected if Custom avatar URLs are permitted and avatars render in the buddy list view.
  4. Inspect buddy list for unsanitized content
    As an administrator, review the buddy list code or view a test account's buddy list to see if avatar URLs are rendered without proper HTML encoding or sanitization.
    Affected if Avatar URLs in the buddy list are rendered without sanitization, allowing raw HTML or script tags to be displayed.

If the installed MyBB version is 1.6.4 or lower and the buddy list feature with custom avatar support is enabled, the environment is likely affected by this stored XSS vulnerability.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 1.6.4
Interim mitigation

Upgrade MyBB to version 1.6.5 or later which includes proper sanitization of avatar data in the buddy list. If immediate upgrade is not possible, consider disabling the buddy list feature or implementing web application firewall rules to detect malicious avatar URL patterns.

Recommended fix High confidence

MyBB 1.6.5 or later (preferably latest 1.6.x stable release)

  1. 1. Back up your MyBB database and all website files before proceeding
  2. 2. Download MyBB version 1.6.5 (or the latest stable 1.6.x release) from the official MyBB website
  3. 3. Extract the downloaded package
  4. 4. Upload all new files to your server, overwriting the existing MyBB installation files
  5. 5. Navigate to your forum's install directory (e.g., yourdomain.com/install/) to run the upgrade script
  6. 6. Follow the on-screen upgrade instructions to complete the database updates
  7. 7. Clear all MyBB caches from the Admin Control Panel
  8. 8. Verify the upgrade was successful by logging into the Admin Control Panel and checking the version number
Caveat Point upgrades typically have minimal breaking changes; however, always test the upgrade in a staging environment first and review custom plugins for compatibility

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Mybb Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,664.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2011-5133 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2011-5133 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data