FirefoxWeb browser · Mozilla
CVE-2026-12312
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 · low confidenceA memory safety bug in Firefox and Thunderbird that could allow for potential memory corruption or exploitation. The specific nature of the memory safety issue (e.g., use-after-free, buffer overflow) is not detailed in the available information.
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
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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 checksWork through these to decide whether this CVE applies to you.
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Check Firefox versionIn Firefox, go to Menu > Help > About Firefox. Alternatively, run: firefox --versionAffected if Installed version is below 140.12.0 or is 140.12.0 through 151.x (i.e., less than 152.0.0)
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Check Thunderbird versionIn Thunderbird, go to Menu > Help > About Thunderbird. Alternatively, run: thunderbird --versionAffected if Installed version is below 140.12.0 or is 140.12.0 through 151.x (i.e., less than 152.0.0)
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Check for Firefox ESR versionIf using Firefox ESR, run: firefox --version or check About Firefox. ESR versions follow a different numbering schemeAffected if ESR version is below 140.12.0
A user is affected if any installed Firefox or Thunderbird version is less than 140.12.0 or falls between 140.12.0 and 151.x inclusive.
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
Upgrade to Firefox 152, Firefox ESR 140.12, Thunderbird 152, or Thunderbird 140.12 or later to address the memory safety vulnerability.
Firefox 152 (or Firefox ESR 140.12); Thunderbird 152 (or Thunderbird 140.12)
- Verify current Firefox or Thunderbird version by navigating to Menu > Help > About (or running 'firefox --version' / 'thunderbird --version' in terminal)
- For Firefox: Download Firefox 152 or later from www.mozilla.org/firefox/ or use your system's package manager to upgrade
- For Firefox ESR: Upgrade to Firefox ESR 140.12 or later
- For Thunderbird: Download Thunderbird 152 or later from www.mozilla.org/thunderbird/ or use your system's package manager to upgrade
- For Thunderbird ESR: Upgrade to Thunderbird 140.12 or later
- Restart the application after upgrade
- Verify the fix by checking the About section shows version 152.x or 140.12.x or higher
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
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
Free · runs locallyCheck whether your project pulls in CVE-2026-12312 — 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-2026-12312 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
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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