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FirefoxWeb browser · Mozilla

CVE-2026-2774

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
Integer overflow in the Audio/Video 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

Integer overflow vulnerability in the Audio/Video processing component of Firefox and Thunderbird. The overflow could potentially allow remote code execution or memory corruption when processing specially crafted media content, given the critical CVSS score of 9.8.

MitigationUpgrade to Firefox 148 (or ESR 115.33/140.8) and Thunderbird 148 (or 140.8) to apply the patch. Organizations should deploy via their patch management infrastructure and verify Audio/Video functionality post-update.

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. Check installed Firefox version
    In Firefox, go to Menu > Help > About Firefox, or enter 'about:support' in the address bar. The version number is displayed at the top.
    Affected if The version is below 115.33.0, or is 128.x through 140.7.x (140.8.0 and above are fixed)
  2. Check installed Thunderbird version
    In Thunderbird, go to Menu > Help > About Thunderbird. The version number is displayed in the window that opens.
    Affected if The version is below 140.8.0 (versions 140.8.0 and above are fixed)
  3. Confirm Audio/Video component is present
    This vulnerability affects the Audio/Video component which is included in standard Firefox and Thunderbird installations. No specific module enablement is required - the component is present by default in both products.
    Affected if The application has the Audio/Video component (this is true for default installations of both Firefox and Thunderbird)

If Firefox is below 115.33.0 or is version 128.x-140.7.x, or if Thunderbird is below 140.8.0, the environment is affected by this integer overflow vulnerability.

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

Upgrade to Firefox 148 (or ESR 115.33/140.8) and Thunderbird 148 (or 140.8) to apply the patch. Organizations should deploy via their patch management infrastructure and verify Audio/Video functionality post-update.

Recommended fix High confidence

Firefox 148.0 (regular), Firefox ESR 115.33.0, Firefox ESR 140.8.0, Thunderbird 140.8.0, or Thunderbird 148.0

  1. 1. Identify the current installed version of Firefox or Thunderbird.
  2. 2. For Firefox regular users: Upgrade to Firefox 148.0 or later.
  3. 3. For Firefox ESR users: If on ESR 115.x, upgrade to Firefox ESR 115.33.0 or later; if on ESR 128.x, upgrade to Firefox ESR 140.8.0 or later.
  4. 4. For Thunderbird users: Upgrade to Thunderbird 140.8.0 or later, or Thunderbird 148.0 or later.
  5. 5. Verify the upgrade was successful by checking the application version (Help > About Firefox/Thunderbird).
Caveat Upgrading to a new major version may introduce compatibility issues with existing extensions or plugins; test in a non-production environment first if applicable.

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,720
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.

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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-2026-2774 in production — separate from our analysis above.

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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