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FirefoxWeb browser · Mozilla

CVE-2026-2788

CRITICAL · 9.8 CVSS v3.1 Published 2026-02-24
Fix available
A fix is available. Upgrade to 115.33.0 / 140.8.0 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
Incorrect boundary conditions in the Audio/Video: GMP component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

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 boundary condition vulnerability in the Gecko Media Plugin (GMP) component used for audio/video processing allows for memory corruption due to incorrect bounds checking when processing media data. This critical flaw in the media handling subsystem could allow an attacker to trigger heap-based buffer overflows or similar memory corruption, potentially enabling remote code execution.

MitigationApply the vendor-supplied patches by updating to Firefox 148, Firefox ESR 115.33/140.8, or Thunderbird 148/140.8 as appropriate for the deployed product.

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:< 115.33.0< 148.0>= 128.0, < 140.8.0
ThunderbirdApplication
Affected:< 140.8.0< 148.0

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. Identify installed Firefox version
    In Firefox, go to Menu > Help > About Firefox, or enter 'about:support' in the address bar. The version is displayed at the top of the page.
    Affected if Version is below 115.33.0, OR between 128.0.0 and 140.7.x inclusive, OR between 141.0.0 and 147.x (any minor version)
  2. Identify installed Thunderbird version
    In Thunderbird, go to Menu > Help > About Thunderbird. The version is displayed at the top of the window.
    Affected if Version is below 140.8.0, OR between 141.0.0 and 147.x (any minor version)
  3. Check if GMP media plugins are enabled
    In Firefox, type 'about:plugins' in the address bar. Look for any GMP (Gecko Media Plugins) entries such as OpenH264, Widevine, or other codec plugins. In Thunderbird, check Tools > Add-ons and Plugins.
    Affected if Any GMP plugin is installed and enabled (the vulnerability exists in the GMP component itself regardless of which plugin is present)

A user is affected if they run Firefox versions listed above OR Thunderbird versions listed above AND have GMP plugins enabled in their browser or email client.

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 115.33.0 / 140.8.0 / 148.0 or later
Fixed in 115.33.0140.8.0148.0
Interim mitigation

Apply the vendor-supplied patches by updating to Firefox 148, Firefox ESR 115.33/140.8, or Thunderbird 148/140.8 as appropriate for the deployed product.

Recommended fix High confidence

Firefox 148 (standard), Firefox ESR 115.33 or 140.8 (ESR branches), Thunderbird 148 or 140.8

  1. Check current Firefox or Thunderbird version via Help > About Firefox/Thunderbird
  2. Download the appropriate fixed version from the official Mozilla website: https://www.mozilla.org/firefox/releases/ or https://www.thunderbird.net/
  3. For Firefox users: Upgrade to Firefox 148, or if on ESR, upgrade to Firefox ESR 115.33 or Firefox ESR 140.8
  4. For Thunderbird users: Upgrade to Thunderbird 148 or Thunderbird 140.8
  5. Restart the application after installation
Caveat Standard upgrade risks apply - test critical workflows before deployment in production environments

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
  • Testing3.0 h
  • Review / QA2.0 h
8.0 hours of engineering $1,370
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,192.

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-2026-2788 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