FirefoxWeb browser · Mozilla
CVE-2016-2826
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 · uneditedThe maintenance service in Mozilla Firefox before 47.0 and Firefox ESR 45.x before 45.2 on Windows does not prevent MAR extracted-file modification during updater execution, which might allow local users to gain privileges via a Trojan horse file.
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 confidenceThe Firefox maintenance service on Windows does not properly protect MAR (Mozilla Archive) extracted files during the updater execution window. A local attacker can replace files during the update process with Trojan horse executables that will be run with elevated (SYSTEM) privileges by the maintenance service, achieving local privilege escalation.
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
= 45.1.0= 45.1.1<= 46.0.1CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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 if Firefox is installed on WindowsCheck for Firefox installation in registry key HKLM\SOFTWARE\Mozilla\Mozilla Firefox or look for firefox.exe in common paths like C:\Program Files\Mozilla Firefox or C:\Program Files (x86)\Mozilla FirefoxAffected if Firefox is found on the system
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Determine the installed Firefox versionCheck the version in the registry at HKLM\SOFTWARE\Mozilla\Mozilla Firefox\CurrentVersion or open Firefox and navigate to about:firefox to view the version numberAffected if The installed version is 45.1.0, 45.1.1, or any version up to and including 46.0.1 (including 46.0 and 46.0.1)
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Check if the Firefox maintenance service existsOpen Services.msc and look for 'Mozilla Maintenance Service' or check registry key HKLM\SYSTEM\CurrentControlSet\Services\MozellaMaintenanceServiceAffected if The Mozilla Maintenance Service is installed and present on the system
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Verify the service runs with elevated privilegesCheck the service properties in Services.msc - the 'Log on as' field typically shows 'Local System' or 'NT AUTHORITY\SYSTEM' for the Mozilla Maintenance ServiceAffected if The maintenance service is configured to run with SYSTEM or elevated privileges
A user is affected if they are running Firefox version 45.1.0, 45.1.1, or any version through 46.0.1 on Windows, and the Mozilla Maintenance Service is installed and runs with elevated privileges.
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 dataDeploy Firefox 47.0 or later (or Firefox ESR 45.2+) to replace vulnerable versions. Ensure the maintenance service runs with least privilege or restrict file system access to the update directory during patching.
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-2016-2826 — 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-2016-2826 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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