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FirefoxWeb browser · Mozilla

CVE-2025-9179

CRITICAL · 9.8 CVSS v3.1 Published 2025-08-19
Fix available
A fix is available. Upgrade to 115.27.0 / 128.14.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges 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
An attacker was able to perform memory corruption in the GMP process which processes encrypted media. This process is also heavily sandboxed, but represents slightly different privileges from the content process. This vulnerability was fixed in Firefox 142, Firefox ESR 115.27, Firefox ESR 128.14, Firefox ESR 140.2, Thunderbird 142, Thunderbird 128.14, and Thunderbird 140.2.

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 confidence

A memory corruption vulnerability exists in Firefox's GMP (Gecko Media Plugin) process, which handles decryption and processing of encrypted media content. While the GMP process runs in a sandbox, it operates with slightly elevated privileges compared to the content process, allowing an attacker to achieve memory corruption that could lead to arbitrary code execution.

MitigationUpdate affected installations to Firefox 142, Firefox ESR 115.27/128.14/140.2, or Thunderbird 142/128.14/140.2. Organizations should deploy these updates through their standard patch management processes.

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:< 115.27.0< 142.0>= 128.0, < 128.14.0>= 140.0, < 140.2.0
ThunderbirdApplication
Affected:< 128.14.0< 142.0>= 140.0, < 140.2.0

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
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/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 Firefox version
    Open Firefox, go to Help > About Firefox (or navigate to about:support). Note the version number displayed.
    Affected if The version is less than 115.27.0, OR between 128.0.0 and 128.13.x inclusive, OR between 140.0.0 and 140.1.x inclusive, OR less than 142.0.
  2. Check Thunderbird version
    Open Thunderbird, go to Help > About Thunderbird. Note the version number displayed.
    Affected if The version is less than 128.14.0, OR between 140.0.0 and 140.1.x inclusive, OR less than 142.0.
  3. Identify if GMP plugins are in use
    Navigate to about:support in Firefox or Thunderbird. Look for 'GMP' entries in the 'Media' or 'Plugins' section. Common GMP plugins include Widevine (CDP), Clearkey, or other DRM-related plugins.
    Affected if Any GMP plugin (Widevine, Clearkey, or similar DRM modules) is listed as installed or active in about:support.
  4. Check for GMP plugin process activity
    In Firefox/Thunderbird, navigate to about:processes. Look for a 'GMP' or 'GeckoMediaPlugin' process entry running alongside the main browser process.
    Affected if A GMP process is actively running, indicating the GMP subsystem is enabled and processing media.

You are affected if you run Firefox or Thunderbird with a version number matching the affected ranges AND have GMP plugins (such as Widevine or Clearkey for DRM content) installed or enabled.

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 115.27.0 / 128.14.0 / 140.2.0 or later
Fixed in 115.27.0128.14.0140.2.0
Interim mitigation

Update affected installations to Firefox 142, Firefox ESR 115.27/128.14/140.2, or Thunderbird 142/128.14/140.2. Organizations should deploy these updates through their standard patch management processes.

Recommended fix High confidence

Firefox 142 / Firefox ESR 115.27+ / Firefox ESR 128.14+ / Firefox ESR 140.2+ / Thunderbird 142 / Thunderbird 128.14+ / Thunderbird 140.2+ (specific version depends on current release channel)

  1. Check current Firefox or Thunderbird version via Help > About Firefox/Thunderbird or running 'firefox --version' or 'thunderbird --version' in terminal
  2. If running Firefox stable < 142.0, upgrade to Firefox 142 or later
  3. If running Firefox ESR 115.x < 115.27.0, upgrade to Firefox ESR 115.27 or later
  4. If running Firefox ESR 128.x < 128.14.0, upgrade to Firefox ESR 128.14 or later
  5. If running Firefox ESR 140.x < 140.2.0, upgrade to Firefox ESR 140.2 or later
  6. If running Thunderbird < 128.14.0, upgrade to Thunderbird 128.14 or later
  7. If running Thunderbird 140.x < 140.2.0, upgrade to Thunderbird 140.2 or later
  8. If running Thunderbird < 142.0, upgrade to Thunderbird 142 or later
Caveat Standard upgrade may include add-on compatibility changes; ensure extensions are compatible with target version

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,664.

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-2025-9179 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