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FirefoxWeb browser · Mozilla

CVE-2026-4694

HIGH · 7.5 CVSS v3.1 Published 2026-03-24
Fix available
A fix is available. Upgrade to 115.34.0 / 140.9.0 or later.
See remediation →
84/100
Remediation priority · High
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, integer overflow in the Graphics component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

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 due to incorrect boundary conditions in the Graphics component of Firefox and Thunderbird. This could allow an attacker to trigger heap-based memory corruption via crafted graphics operations, potentially leading to code execution or denial of service.

MitigationUpdate Mozilla products to the fixed versions: Firefox 149 (or ESR 115.34/140.9), Thunderbird 149 (or 140.9). Prioritize affected systems based on exposure to untrusted content.

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:< 115.34.0< 149.0>= 128.0, < 140.9.0
ThunderbirdApplication
Affected:< 140.9.0< 149.0

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.
    Affected if The installed version is earlier than 115.34.0, OR falls between 128.0 and 140.8.x inclusive, OR is earlier than 149.0 (all versions below 149.0 are affected)
  2. Identify installed Thunderbird version
    In Thunderbird, go to Menu > Help > About Thunderbird. The version number is shown in the window that opens.
    Affected if The installed version is earlier than 140.9.0 OR earlier than 149.0 (all versions below 149.0 are affected)
  3. Confirm graphics rendering is enabled
    This vulnerability exists in the Graphics component handling graphical operations. No special configuration needs to be checked; the vulnerability triggers during normal graphics processing in affected versions.
    Affected if Any use of the browser orThunderbird with graphical content rendering (this includes normal web browsing and email viewing)
  4. Check for multiple affected Mozilla installations
    On systems with multiple Firefox installations (such as Firefox and Firefox ESR), verify the version of each installation separately using 'about:support' or checking the application file properties.
    Affected if Any Firefox ESR or Thunderbird installation matches the affected version ranges

You are affected if you run any version of Firefox below 115.34.0, below 140.9.0, or below 149.0 (or any version of Thunderbird below 140.9.0 or 149.0), as all these versions contain the vulnerable graphics component code.

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 115.34.0 / 140.9.0 / 149.0 or later
Fixed in 115.34.0140.9.0149.0
Interim mitigation

Update Mozilla products to the fixed versions: Firefox 149 (or ESR 115.34/140.9), Thunderbird 149 (or 140.9). Prioritize affected systems based on exposure to untrusted content.

Recommended fix High confidence

Firefox 149 (stable), Firefox ESR 115.34, Firefox ESR 140.9; Thunderbird 149 or 140.9

  1. Check current Firefox or Thunderbird version by navigating to Menu > Help > About (or typing 'about:support' in the address bar)
  2. If using Firefox stable: upgrade to version 149 or later
  3. If using Firefox ESR 128.x: upgrade to Firefox ESR 140.9 or later
  4. If using Firefox ESR 115.x: upgrade to Firefox ESR 115.34 or later
  5. If using Thunderbird stable: upgrade to version 149 or later
  6. If using Thunderbird ESR: upgrade to version 140.9 or later
  7. Restart the application after upgrading
  8. Verify the fix by checking the updated version number in About
Caveat Standard minor version upgrades typically maintain compatibility; review release notes for any add-on or extension compatibility changes

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2026-4694 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