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FirefoxWeb browser · Mozilla

CVE-2026-4706

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 in the Graphics: Canvas2D 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

A boundary condition vulnerability in Mozilla's Canvas2D graphics rendering component allows incorrect bounds checking, potentially leading to memory safety issues such as out-of-bounds read or write operations. This client-side flaw in the browser's graphics engine could be triggered by malicious web content.

MitigationDeploy the fixed versions of Firefox (149, ESR 115.34, ESR 140.9) or Thunderbird (149, 140.9) to all affected endpoints. Organizations should use their patch management systems to push these updates enterprise-wide.

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

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. Confirm Firefox installation
    Check if Mozilla Firefox is installed by looking for the executable or checking system installed packages. On Windows, check Program Files or Program Files (x86)\Mozilla Firefox. On Linux, check /usr/bin/firefox or package manager. On macOS, check /Applications/Firefox.app.
    Affected if Firefox is installed on the system
  2. Identify installed Firefox version
    Open Firefox, go to Help > About Firefox, or run 'firefox --version' from command line. On Windows, right-click Firefox shortcut and check properties, or read the version from the executable metadata.
    Affected if The installed version is revealed
  3. Compare version against affected ranges
    The affected version ranges are: < 115.34.0, 128.0 through < 140.9.0, and < 149.0 (for non-ESR versions). Note that versions 115.34.0 through 127.x are also affected since they are < 149.0. Compare your installed version number against these ranges.
    Affected if Installed version falls into any of these ranges: below 115.34.0, between 128.0 and 140.8.x, or between 115.34.0 and 148.x (for non-ESR releases)
  4. Check if using ESR branch
    If Firefox is installed, determine if it is the ESR (Extended Support Release) version by checking Help > About Firefox - ESR versions include 'ESR' in the version string, or check the package/install source.
    Affected if ESR versions below 115.34.0 or below 140.9.0 are affected

You are affected if Firefox is installed and the installed version is any version below 115.34.0 (ESR or standard), any version from 128.0 to 140.8.x, or any standard release below 149.0.

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

Deploy the fixed versions of Firefox (149, ESR 115.34, ESR 140.9) or Thunderbird (149, 140.9) to all affected endpoints. Organizations should use their patch management systems to push these updates enterprise-wide.

Recommended fix High confidence

Firefox 149 (Main Release) or Firefox ESR 115.34 or Firefox ESR 140.9 depending on your release track

  1. Determine if you are running Firefox Main Release or Firefox ESR by checking Help > About Firefox
  2. For Firefox Main Release users: Upgrade to Firefox 149 or later
  3. For Firefox ESR 115.x users: Upgrade to Firefox ESR 115.34 or later
  4. For Firefox ESR 128.x and 140.x users: Upgrade to Firefox ESR 140.9 or later
  5. After upgrade, verify the version by navigating to Help > About Firefox to confirm the installed version
Caveat Mozilla Firefox upgrades typically have minimal breaking changes; however, some legacy add-ons or extensions may be incompatible with newer major versions

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
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,424.

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-2026-4706 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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