FirefoxWeb browser · Mozilla
CVE-2015-0821
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 36.0 allows user-assisted remote attackers to read arbitrary files or execute arbitrary JavaScript code with chrome privileges via a crafted web site that is accessed with unspecified mouse and keyboard actions.
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 confidenceMozilla Firefox before 36.0 contains a vulnerability where a crafted website, when accessed with specific mouse and keyboard actions by the user, allows remote attackers to read arbitrary files on the system or execute arbitrary JavaScript code with chrome (full browser) privileges. The user-assisted aspect means the victim must interact with the malicious page in an unspecified way.
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
<= 35.0.1= 0.1= 0.2= 0.3= 0.4= 0.5= 0.6= 0.6.1= 0.7= 0.7.1= 0.8= 0.9
Ubuntu LinuxOperating system
= 12.04= 14.04= 14.10= 13.1= 13.2CVSS 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
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:M/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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Verify Firefox is installedCheck for Firefox installation: On Linux run 'which firefox' or look in /usr/bin/firefox; On Windows check C:\Program Files\Mozilla Firefox\firefox.exe; On macOS check /Applications/Firefox.appAffected if Firefox is not installed on the system
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Determine installed Firefox version on LinuxRun 'firefox --version' or check the package manager: On Ubuntu/Debian run 'dpkg -l | grep firefox'; On OpenSUSE run 'rpm -qi firefox'Affected if Version displayed is less than 36.0 (for example 35.0.1, 35.0, or any version listed in affected ranges like 0.1 through 0.9)
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Determine installed Firefox version on WindowsOpen Firefox, click Help > About Firefox, or check the file properties of firefox.exe in the installation directoryAffected if Version shown is 35.0.1 or earlier (versions below 36.0)
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Confirm Ubuntu system package versionRun 'apt-cache policy firefox' on Ubuntu systems to see installed and available versions of the Firefox packageAffected if The installed version string indicates a version prior to 36.0
The system is affected if Mozilla Firefox is installed and its version is less than 36.0, as versions 35.0.1 and earlier contain the file read and code execution vulnerability requiring user interaction.
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 dataUpgrade Firefox to version 36.0 or later. This is a client-side browser vulnerability; organizations should ensure browser update management is in place.
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-2015-0821 — 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-2015-0821 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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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.
- 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