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FirefoxWeb browser · Mozilla

CVE-2011-3647

HIGH · 9.3 CVSS v2.0 Published 2011-11-09
Fix available
A fix is available. Upgrade to after 3.6.23 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
The JSSubScriptLoader in Mozilla Firefox before 3.6.24 and Thunderbird before 3.1.6 does not properly handle XPCNativeWrappers during calls to the loadSubScript method in an add-on, which makes it easier for remote attackers to gain privileges via a crafted web site that leverages certain unwrapping behavior, a related issue to CVE-2011-3004.

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 · high confidence

The JSSubScriptLoader in Firefox before 3.6.24 and Thunderbird before 3.1.6 fails to properly handle XPCNativeWrappers when the loadSubScript method is called by add-ons. This allows a malicious website to bypass security wrapper protections and execute code with elevated privileges, enabling remote code execution or privilege escalation attacks.

MitigationUpgrade affected systems to Firefox 3.6.24 or later, or Thunderbird 3.1.6 or later. For legacy systems that cannot upgrade, consider replacing with supported browser versions or implementing network-level blocking of untrusted websites.

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
FirefoxWeb browser
Affected:<= 3.6.23= 0.1= 0.2= 0.3= 0.4= 0.5= 0.6= 0.6.1= 0.7= 0.7.1= 0.8= 0.9
ThunderbirdApplication
Affected:<= 3.1.5= 0.1= 0.2= 0.3= 0.4= 0.5= 0.6= 0.7= 0.7.1= 0.7.2= 0.7.3= 0.8

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
M
Authentication
None
Confidentiality
Complete
Integrity
Complete
Availability
Complete

AV:N/AC:M/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 Mozilla product
    Check for Firefox or Thunderbird installation by examining program directories (e.g., C:\Program Files\Mozilla Firefox or C:\Program Files\Mozilla Thunderbird on Windows, /Applications/Firefox or /Applications/Thunderbird on macOS, /usr/lib/firefox or /usr/lib/thunderbird on Linux)
    Affected if Neither Firefox nor Thunderbird is installed on the system
  2. Determine Firefox version
    For Firefox: open Help > About Firefox, or check version.json in the installation directory, or run 'firefox --version' from command line
    Affected if Installed version is 3.6.23 or earlier, or falls within versions 0.1 through 0.9 (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.6.1, 0.7, 0.7.1, 0.8, 0.9)
  3. Determine Thunderbird version
    For Thunderbird: open Help > About Thunderbird, or check version.json in the installation directory, or run 'thunderbird --version' from command line
    Affected if Installed version is 3.1.5 or earlier, or falls within versions 0.1 through 0.8 (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.7.1, 0.7.2, 0.7.3, 0.8)
  4. Confirm add-on usage (optional context)
    Examine installed add-ons in the profiles folder (e.g., %APPDATA%\Mozilla\Firefox\Profiles\*.default\extensions on Windows) for extensions that may use the loadSubScript JavaScript method
    Affected if Extensions using loadSubScript are present and the browser version falls within affected ranges - this indicates potential exploitability in a web browsing context

A system is affected if Firefox version 3.6.23 or earlier (including 0.x series up to 0.9) or Thunderbird version 3.1.5 or earlier (including 0.x series up to 0.8) is installed and the user runs untrusted websites or has add-ons that leverage the loadSubScript method.

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 3.6.23
Interim mitigation

Upgrade affected systems to Firefox 3.6.24 or later, or Thunderbird 3.1.6 or later. For legacy systems that cannot upgrade, consider replacing with supported browser versions or implementing network-level blocking of untrusted websites.

Recommended fix High confidence

Firefox 3.6.24 or later; Thunderbird 3.1.6 or later

  1. 1. Verify current Firefox version by navigating to Help > About Mozilla Firefox
  2. 2. Verify current Thunderbird version by navigating to Help > About Mozilla Thunderbird
  3. 3. For Firefox: Download and install Firefox 3.6.24 or later from the official Mozilla website (https://www.mozilla.org/firefox/)
  4. 4. For Thunderbird: Download and install Thunderbird 3.1.6 or later from the official Mozilla website (https://www.thunderbird.net/)
  5. 5. After installation, restart the application
  6. 6. Verify the update was successful by checking the version number again
Caveat These are older legacy versions; consider upgrading to a modern supported release (Firefox ESR or current stable) for continued security support

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
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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-2011-3647 in production — separate from our analysis above.

No notes yet

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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