FirefoxWeb browser · Mozilla
CVE-2016-5293
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 · uneditedWhen the Mozilla Updater is run, if the Updater's log file in the working directory points to a hardlink, data can be appended to an arbitrary local file. This vulnerability requires local system access. Note: this issue only affects Windows operating systems. This vulnerability affects Firefox ESR < 45.5 and Firefox < 50.
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 vulnerability in Mozilla Updater allows an attacker with local system access to append data to arbitrary files by pointing the updater's log file path to a hardlink. When the updater runs, it follows the hardlink and writes log data to the target file, enabling local privilege escalation or data modification on Windows systems.
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
< 45.5.0< 50.0
Debian LinuxOperating system
= 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
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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Confirm Firefox is installedCheck for Firefox installation: On Windows, look for Firefox in Program Files or check registry. On Linux (Debian 8), run 'dpkg -l | grep firefox' or 'rpm -qa | grep firefox'.Affected if Firefox is present on the system
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Identify installed Firefox versionOn Windows, check Help > About Firefox or inspect the version file in the Firefox directory. On Debian, run 'dpkg -l firefox' or check the version via 'firefox --version'.Affected if A version number is returned
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Compare version against affected rangesCompare your installed version to: Firefox < 45.5.0 or < 50.0 are vulnerable. Note that ESR versions below 45.5.0 are affected, and regular Firefox versions below 50.0 are affected.Affected if Version is less than 45.5.0 (ESR) or less than 50.0 (regular release)
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Verify Debian 8 Mozilla package version (if applicable)On Debian 8 systems, run 'apt-cache policy firefox-esr' or check installed package version with 'dpkg -s firefox-esr'.Affected if Running Debian 8.0 with Firefox ESR version < 45.5
Your system is affected if Firefox is installed with a version below 45.5.0 (ESR) or below 50.0 (regular), allowing a local attacker with system access to exploit the updater hardlink vulnerability.
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 data45.5.050.0
Update Firefox ESR to version 45.5 or later, or Firefox to version 50 or later. This is a standard patch deployment; no workarounds are available for this hardlink-based file write vulnerability.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 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 $1,744.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-5293 — 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-2016-5293 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
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