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FirefoxWeb browser · Mozilla

CVE-2025-6426

HIGH · 8.8 CVSS v3.1 Published 2025-06-24
Fix available
A fix is available. Upgrade to 128.12.0 / 140.0 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges

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 executable file warning did not warn users before opening files with the `terminal` extension. *This bug only affects Firefox for macOS. Other versions of Firefox are unaffected.*. This vulnerability was fixed in Firefox 140, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

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

Firefox for macOS failed to display the executable file warning when opening files with the .terminal extension, allowing potentially malicious executables to run without user warning. This bypasses a security control meant to protect users from unintentionally executing code.

MitigationUpdate affected installations to Firefox 140+, Firefox ESR 128.12+, Thunderbird 140+, or Thunderbird 128.12+ to receive the patched version that includes the executable warning for .terminal files.

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:< 128.12.0< 140.0

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
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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. Verify Firefox is installed
    On macOS, check if /Applications/Firefox.app exists, or run 'ls /Applications | grep -i firefox' in Terminal
    Affected if Firefox application is not found in /Applications directory
  2. Determine installed Firefox version
    Run 'defaults read /Applications/Firefox.app/Contents/Info.plist CFBundleShortVersionString' in Terminal, or click Firefox > About Firefox in the menu bar
    Affected if Cannot determine Firefox version from the installed application
  3. Compare version against affected ranges
    Compare the installed version number to the affected ranges: versions < 128.12.0 or versions < 140.0
    Affected if Installed version is 128.x below 128.12.0, or 140.x below 140.0, or any version in the 139.x range or earlier not meeting these thresholds
  4. Confirm macOS platform
    Run 'sw_vers -productVersion' in Terminal to verify the operating system is macOS
    Affected if System is not running macOS (this vulnerability specifically affects Firefox on macOS)

A user is affected if they are running Firefox on macOS with a version lower than 128.12.0 (for ESR 128.x branches) or lower than 140.0 (for 140.x branches), and the executable file warning bypass for .terminal files would apply to their environment.

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.

dbcve · scoped
Upgrade available Upgrade to 128.12.0 / 140.0 or later
Fixed in 128.12.0140.0
Interim mitigation

Update affected installations to Firefox 140+, Firefox ESR 128.12+, Thunderbird 140+, or Thunderbird 128.12+ to receive the patched version that includes the executable warning for .terminal files.

Recommended fix High confidence

Firefox 140 (stable) or Firefox ESR 128.12

  1. 1. Open Firefox and navigate to Help > About Firefox to check the current version.
  2. 2. If the version is below 140.0 (or below 128.12.0 for ESR), download Firefox 140 (or Firefox ESR 128.12) from the official Mozilla website: https://www.mozilla.org/en-US/firefox/releases/
  3. 3. Close all Firefox windows and tabs.
  4. 4. Install the downloaded Firefox version, following the on-screen prompts.
  5. 5. After installation, restart Firefox and verify the version is 140.0 or later (or 128.12.x for ESR) via Help > About Firefox.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 hours of engineering $750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.

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-2025-6426 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