FirefoxWeb browser · Mozilla
CVE-2026-12305
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 · uneditedMemory safety bug fixed in Firefox 152. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.
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 confidenceA memory safety vulnerability in Firefox and Thunderbird was addressed in versions 152 (Firefox/Thunderbird) and 140.12 (Firefox ESR/Thunderbird ESR). The specific nature of the memory safety issue (e.g., buffer overflow, use-after-free, heap overflow) is not detailed in the available advisory, but such bugs can potentially lead to remote code execution or information disclosure.
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
< 140.12.0< 152.0.0< 140.12.0< 152.0.0CVSS 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 checksWork through these to decide whether this CVE applies to you.
-
Identify installed Firefox versionRun 'firefox --version' in terminal or check Help > About Firefox in the application menuAffected if version is below 140.12.0 or below 152.0.0 (for non-ESR releases)
-
Identify installed Thunderbird versionRun 'thunderbird --version' in terminal or check Help > About Thunderbird in the application menuAffected if version is below 140.12.0 or below 152.0.0 (for non-ESR releases)
-
Determine if running ESR releaseCheck the version string: ESR releases include 'ESR' in the version name (e.g., 140.12.0esr). Alternatively, on Linux check package with 'dpkg -l | grep firefox' or 'rpm -qi firefox'Affected if ESR version is below 140.12.0; non-ESR version is below 152.0.0
The environment is affected if Firefox or Thunderbird is installed with any version below 140.12.0 (ESR) or below 152.0.0 (regular release).
Generated from the published advisory. Verify against your own configuration.
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 · scoped140.12.0152.0.0
Update affected installations to Firefox 152, Firefox ESR 140.12, Thunderbird 152, or Thunderbird 140.12 or later to remediate this vulnerability.
Firefox 152 (or latest), Firefox ESR 140.12+, Thunderbird 152 (or latest), Thunderbird ESR 140.12+
- Check current Firefox or Thunderbird version via Help > About (or thunderbird -v command)
- For Firefox: Visit https://www.mozilla.org/firefox/download/ and download the latest version, or use Help > Check for Updates
- For Thunderbird: Visit https://www.thunderbird.net/ and download the latest version, or use Help > Check for Updates
- Install the updated version and restart the application
- Alternatively, for enterprise deployments, deploy Firefox ESR 140.12 or Thunderbird ESR 140.12 from https://www.mozilla.org/en-US/firefox/enterprise/
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
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-12305 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-12305 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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.
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.
- 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