FirefoxWeb browser · Mozilla
CVE-2011-3661
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 · uneditedYARR, as used in Mozilla Firefox 4.x through 8.0, Thunderbird 5.0 through 8.0, and SeaMonkey before 2.6, allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via crafted JavaScript.
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 confidenceA memory corruption vulnerability in the YARR (Yet Another Regular Regexp) JavaScript regular expression engine used in Mozilla Firefox, Thunderbird, and SeaMonkey allows remote attackers to crash the application or potentially execute arbitrary code via specially crafted JavaScript containing malicious regex 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
FirefoxWeb browser
= 4.0= 4.0.1= 5.0= 5.0.1= 6.0= 6.0.1= 6.0.2= 7.0= 7.0.1= 8.0<= 2.5= 1.0= 1.0.1= 1.0.2= 1.0.3= 1.0.4= 1.0.5= 1.0.6= 1.0.7= 1.0.8= 1.0.9= 1.0.99= 5.0= 6.0= 6.0.1= 6.0.2= 7.0= 7.0.1= 8.0CVSS 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
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:L/Au:N/C:P/I:P/A:P
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 checksWork through these to decide whether this CVE applies to you.
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Identify installed Mozilla product and versionFor Firefox: go to Help > About Firefox. For Thunderbird: go to Help > About Thunderbird. For SeaMonkey: go to Help > About SeaMonkey. Alternatively, check the application binary or package version.Affected if The product is Firefox 4.0-8.0, Thunderbird 5.0-8.0, or SeaMonkey 1.x through 2.5 (or 2.5 and below)
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Confirm JavaScript is enabledIn Firefox: check Options > Content > Enable JavaScript. In Thunderbird: Options > Security > Enable JavaScript (note: Thunderbird disables JS by default for security). In SeaMonkey: Preferences > Privacy & Security > Enable JavaScript.Affected if JavaScript is enabled in the application settings, allowing web content or邮件 to execute JavaScript code containing malicious regex patterns
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Verify YARR regex engine is in useThe YARR engine is built into the JavaScript engine of affected versions. There is no user-facing toggle. To confirm, inspect the application binaries or check about:config for js>regex (no direct config exists for this engine).Affected if The application uses the built-in JavaScript engine with YARR for regex processing, which is the default behavior in all affected versions
You are affected if you are running Firefox 4.0-8.0, Thunderbird 5.0-8.0, or SeaMonkey 1.x-2.5 AND JavaScript is enabled, allowing specially crafted regex patterns to trigger memory corruption in the YARR engine.
Generated from the published advisory. Verify against your own configuration.
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.
From vendor dataApply the appropriate security updates released by Mozilla for Firefox 8.0+, Thunderbird 8.0+, and SeaMonkey 2.6+ to address the YARR vulnerability.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2011-3661 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2011-3661 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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