FirefoxWeb browser · Mozilla
CVE-2012-3989
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 · uneditedMozilla Firefox before 16.0, Thunderbird before 16.0, and SeaMonkey before 2.13 do not properly perform a cast of an unspecified variable during use of the instanceof operator on a JavaScript object, which allows remote attackers to execute arbitrary code or cause a denial of service (assertion failure) via a crafted web site.
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 confidenceThis is a type confusion vulnerability in Mozilla Firefox, Thunderbird, and SeaMonkey where the JavaScript instanceof operator improperly casts an unspecified variable, allowing remote attackers to execute arbitrary code or cause a denial of service via crafted 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
< 16.0
Ubuntu LinuxOperating system
= 10.04= 11.04= 11.10= 12.04< 2.13< 16.0= 10= 11= 10= 11CVSS 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 checksWork through these to decide whether this CVE applies to you.
-
Check Firefox versionRun 'firefox --version' or go to Firefox menu > Help > About Firefox to see the installed version numberAffected if Version is below 16.0 (for example, 15.0.1, 15.0, 14.x, etc.)
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Check Thunderbird versionRun 'thunderbird --version' or go to Thunderbird menu > Help > About Thunderbird to see the installed version numberAffected if Version is below 16.0 (for example, 15.x, 14.x, etc.)
-
Check SeaMonkey versionRun 'seamonkey --version' or go to SeaMonkey menu > Help > About SeaMonkey to see the installed version numberAffected if Version is below 2.13 (for example, 2.12, 2.11, etc.)
You are affected if any of Firefox, Thunderbird, or SeaMonkey is installed with a version lower than 16.0 (Firefox/Thunderbird) or 2.13 (SeaMonkey), as the JavaScript instanceof type confusion flaw can be triggered by malicious websites.
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.
dbcve · scoped2.1316.0
Update affected Mozilla products to Firefox 16.0+, Thunderbird 16.0+, or SeaMonkey 2.13 or later to remediate this vulnerability.
Firefox 16.0, Thunderbird 16.0, or SeaMonkey 2.13 (depending on product)
- For Firefox users: Upgrade to Firefox 16.0 or later via the official Mozilla download page or system package manager
- For Thunderbird users: Upgrade to Thunderbird 16.0 or later via the official Mozilla download page or system package manager
- For SeaMonkey users: Upgrade to SeaMonkey 2.13 or later via the official SeaMonkey download page
- For Linux systems (Ubuntu 10.04, 11.04, 11.10, 12.04; SUSE Linux Enterprise Desktop/Server 10, 11): Run system update (e.g., 'apt-get update && apt-get upgrade' for Ubuntu, or 'zypper update' for SUSE) to receive the patched Mozilla packages
Generated from the published advisory — verify against the referenced sources before acting.
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-2012-3989 — 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-2012-3989 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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