FirefoxWeb browser · Mozilla
CVE-2014-1540
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 · uneditedUse-after-free vulnerability in the nsEventListenerManager::CompileEventHandlerInternal function in the Event Listener Manager in Mozilla Firefox before 30.0 allows remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via crafted web content.
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 confidenceUse-after-free vulnerability in Mozilla Firefox's Event Listener Manager (nsEventListenerManager::CompileEventHandlerInternal) allows remote attackers to execute arbitrary code or cause heap memory corruption via crafted malicious web content. The flaw occurs when the browser processes specially crafted JavaScript event handlers that reference freed memory objects.
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
<= 29.0.1CVSS 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.
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Check installed Firefox versionOpen Firefox, click Help > About Firefox (or navigate to about:support). Locate the version number displayed.Affected if The version shown is 29.0.1 or any earlier version (for example, 29.0, 28.0, 27.0, etc.)
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Verify browser is not the patched releaseConfirm the exact version number in the About dialog. Version 30.0 and later contain the fix.Affected if The version is 29.0.1 or lower, indicating an unpatched browser.
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Confirm JavaScript and Event Handler processing is enabledIn Firefox, go to Options > Privacy & Security (or Options > Content in older versions). Ensure JavaScript is enabled (this is the default setting).Affected if JavaScript is enabled, which is required for the malicious event handler code to execute.
A user is affected if they are running Firefox version 29.0.1 or earlier with JavaScript enabled, as the use-after-free flaw in the Event Listener Manager can be triggered by visiting crafted malicious web pages.
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 · scopedUpgrade Firefox to version 30.0 or later to obtain the patched binary. Until then, restrict web browsing to trusted sites and consider using an alternative browser for untrusted web activity.
Firefox 30.0 or later
- Upgrade Mozilla Firefox to version 30.0 or later to address the use-after-free vulnerability in nsEventListenerManager::CompileEventHandlerInternal
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
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,424.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2014-1540 — 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-2014-1540 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
- No weaponised exploit code, or anything meant to cause harm
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