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FirefoxWeb browser · Mozilla

CVE-2026-4719

HIGH · 7.5 CVSS v3.1 Published 2026-03-24
Fix available
A fix is available. Upgrade to 140.9.0 / 149.0 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: Text component. This vulnerability was fixed in Firefox 149, 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

Vulnerability in the Graphics: Text component of Firefox and Thunderbird caused by incorrect boundary conditions, which could allow memory corruption or out-of-bounds access when processing text rendering operations.

MitigationUpdate affected installations to Firefox 149, Firefox ESR 140.9, Thunderbird 149, or Thunderbird 140.9 to obtain the patched version.

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:< 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. Check Firefox installed version
    Navigate to Firefox menu > Help > About Firefox, or enter 'about:support' in the address bar. The version number is displayed at the top of the page.
    Affected if The installed version is below 140.9.0, or is between 140.9.0 and 149.0 (exclusive)
  2. Check Thunderbird installed version
    Navigate to Thunderbird menu > Help > About Thunderbird, or enter 'about:support' in the address bar. The version number is displayed at the top of the page.
    Affected if The installed version is below 140.9.0, or is between 140.9.0 and 149.0 (exclusive)
  3. Verify text rendering is in use
    This vulnerability affects text rendering operations within the Graphics: Text component. Any usage of Firefox or Thunderbird that involves displaying or rendering text will trigger the affected code path.
    Affected if The application is actively used for any text display, email viewing, or web browsing - the vulnerability is in the core text rendering engine and does not require specific configuration to be triggered

A user is affected if they have Firefox or Thunderbird installed with any version prior to 140.9.0, or any version from 140.9.0 up to but not including 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 140.9.0 / 149.0 or later
Fixed in 140.9.0149.0
Interim mitigation

Update affected installations to Firefox 149, Firefox ESR 140.9, Thunderbird 149, or Thunderbird 140.9 to obtain the patched version.

Recommended fix High confidence

Firefox 149.0+, Firefox ESR 140.9+, Thunderbird 140.9+, or Thunderbird 149+

  1. 1. Open Firefox and navigate to Help > About Firefox (or Menu > Help > About Firefox)
  2. 2. The browser will automatically check for updates and prompt you to download version 149.0 or later
  3. 3. Alternatively, download Firefox 149.0 or later from the official Mozilla website: https://www.mozilla.org/firefox/releases/
  4. 4. For Enterprise deployments using Firefox ESR, upgrade to Firefox ESR 140.9 or later
  5. 5. If using Thunderbird, upgrade to Thunderbird 140.9 or Thunderbird 149
  6. 6. Restart the browser after installation to apply the update
  7. 7. Verify the installed version by navigating to Help > About to confirm you are on version 149.0+ or ESR 140.9+

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 hours of engineering $750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.

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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-2026-4719 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