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FirefoxWeb browser · Mozilla

CVE-2026-8969

HIGH · 8.1 CVSS v3.1 Published 2026-05-19
Fix available
A fix is available. Upgrade to 151.0.0 or later.
See remediation →
88/100
Remediation priority · High
Remotely reachable No privileges

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
Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.

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 mitigation bypass in the DOM security component of Firefox and Thunderbird. This vulnerability allows attackers to circumvent security protections in the browser's Document Object Model, potentially enabling further exploitation. The issue was addressed in Firefox 151 and Thunderbird 151.

MitigationUpdate Firefox to version 151 or later, and Thunderbird to version 151 or later. Ensure automatic updates are enabled for continuous protection.

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:< 151.0.0
ThunderbirdApplication
Affected:< 151.0.0

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
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

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 Mozilla product
    Check if Firefox or Thunderbird is installed on the system by looking for the application in the system menu, about dialog, or running 'firefox --version' or 'thunderbird --version' in the command line
    Affected if Neither Firefox nor Thunderbird is installed, then the system is not affected by this CVE for those products
  2. Determine Firefox version
    Open Firefox, go to Help > About Firefox, or run 'firefox --version' in the command line to display the installed version number
    Affected if The displayed version is below 151.0.0 (for example, 150.x, 150.0.x, or earlier)
  3. Determine Thunderbird version
    Open Thunderbird, go to Help > About Thunderbird, or run 'thunderbird --version' in the command line to display the installed version number
    Affected if The displayed version is below 151.0.0 (for example, 150.x, 150.0.x, or earlier)
  4. Verify version format for comparison
    Ensure the version number follows the format major.minor.patch (for example, 150.0.1 or 150.1). Compare numerically: any version where the major number is less than 151 indicates the installed version is in the affected range
    Affected if The major version number is 150 or lower

The environment is affected if Mozilla Firefox or Thunderbird is installed with a version number lower than 151.0.0.

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 151.0.0 or later
Fixed in 151.0.0
Interim mitigation

Update Firefox to version 151 or later, and Thunderbird to version 151 or later. Ensure automatic updates are enabled for continuous protection.

Recommended fix High confidence

Firefox 151.0.0 and Thunderbird 151.0.0

  1. 1. Back up any important data and bookmarks in Firefox/Thunderbird
  2. 2. Open Firefox or Thunderbird application
  3. 3. Navigate to the application menu and select 'Help' > 'About Firefox' or 'About Thunderbird'
  4. 4. The application will automatically check for and install updates to version 151.0.0
  5. 5. Alternatively, download Firefox 151.0.0 or Thunderbird 151.0.0 directly from the official Mozilla website (www.mozilla.org)
  6. 6. Run the installer and restart the application after installation
  7. 7. Verify the installed version by checking 'Help' > 'About' to confirm version 151.0.0 is running
Caveat Review Mozilla's release notes for version 151 for any compatibility notes or deprecated features

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.

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-2026-8969 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