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FirefoxWeb browser · Mozilla

CVE-2019-11736

HIGH · 7.0 CVSS v3.1 Published 2019-09-27
Fix available
A fix is available. Upgrade to 68.1.0 / 69.0 or later.
See remediation →
72/100
Remediation priority · Elevated
Zero-click

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 · unedited
The Mozilla Maintenance Service does not guard against files being hardlinked to another file in the updates directory, allowing for the replacement of local files, including the Maintenance Service executable, which is run with privileged access. Additionally, there was a race condition during checks for junctions and symbolic links by the Maintenance Service, allowing for potential local file and directory manipulation to be undetected in some circumstances. This allows for potential privilege escalation by a user with unprivileged local access. <br>*Note: These attacks requires local system access and only affects Windows. Other operating systems are not affected.*. This vulnerability affects Firefox < 69 and Firefox ESR < 68.1.

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 confidence

The Mozilla Maintenance Service on Windows fails to guard against hardlinked files in the updates directory and contains a race condition during junction/symbolic link checks. This allows an unprivileged local attacker to replace the Maintenance Service executable (which runs with elevated privileges), enabling local privilege escalation.

MitigationUpgrade Firefox to version 69 or later and Firefox ESR to 68.1 or later. This vulnerability is patched in the newer versions.

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
Affected:< 69.0
Firefox EsrWeb browser
Affected:< 68.1.0

CVSS 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
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check if Firefox is installed on Windows
    Open Control Panel > Programs and Features, or run 'Get-ItemProperty HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall\* | Where-Object {$_.DisplayName -like "*Firefox*"}' in PowerShell
    Affected if Firefox is not installed, or the installed version is 69.0 or higher, or 68.1.0 or higher for ESR - if any of these are true, the environment is NOT affected by this specific flaw
  2. Determine the installed Firefox version
    Open Firefox, go to Help > About Firefox, or check the version via registry at HKLM:\SOFTWARE\Mozilla\Mozilla Firefox\CurrentVersion
    Affected if The installed version is less than 69.0 (for standard Firefox) or less than 68.1.0 (for Firefox ESR)
  3. Verify the Mozilla Maintenance Service exists
    Check for the service by running 'Get-Service -Name MozillaMaintenance' in PowerShell, or look for 'C:\Program Files (x86)\Mozilla Maintenance Service\maintenanceservice.exe'
    Affected if The Mozilla Maintenance Service is installed and present on the system (this is required for the vulnerability to apply)
  4. Check if the updates directory exists
    Look for the Firefox updates folder, typically located at '%ProgramData%\Mozilla\updates' or '%AppData%\Local\Mozilla\Firefox\Profiles\*\updates'
    Affected if The updates directory exists and is writable by the current user - this is where the hardlink/symlink attack would occur

A Windows user is affected if they have Firefox versions below 69.0 (or below 68.1.0 for ESR) AND the Mozilla Maintenance Service is installed on their system.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Upgrade available Upgrade to 68.1.0 / 69.0 or later
Fixed in 68.1.069.0
Interim mitigation

Upgrade Firefox to version 69 or later and Firefox ESR to 68.1 or later. This vulnerability is patched in the newer versions.

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA3.0 h
17.0 hours of engineering $2,980
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,768.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2019-11736 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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