FirefoxWeb browser · Mozilla
CVE-2026-12310
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 was fixed in versions 152 and 140.12 respectively. Memory safety bugs in browsers typically involve improper memory handling (such as buffer overflows, use-after-free, or double-free conditions) that could potentially allow remote code execution or memory disclosure. The fix was applied across Firefox, Firefox ESR, and Thunderbird products.
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 installed versionOpen Firefox, click the menu (three lines) > Help > About Firefox, or run `firefox --version` in terminalAffected if Version is below 140.12.0 OR version is 140.12.0 through 151.x (not including 152.0.0)
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Check Thunderbird installed versionOpen Thunderbird, click the menu > Help > About Thunderbird, or run `thunderbird --version` in terminalAffected if Version is below 140.12.0 OR version is 140.12.0 through 151.x (not including 152.0.0)
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Verify if running an affected ESR releaseCheck the version as above - ESR versions display 'ESR' in the version string (e.g., 140.11.2 ESR)Affected if ESR version is below 140.12.0
A user is affected if they run any Firefox or Thunderbird version below 140.12.0, or any version from 140.12.0 up to but not including 152.0.0.
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
Apply the security updates by upgrading to Firefox 152, Firefox ESR 140.12, Thunderbird 152, or Thunderbird 140.12, or later versions.
Firefox 152 / Firefox ESR 140.12 / Thunderbird 152 / Thunderbird ESR 140.12
- Identify the current installed version of Firefox or Thunderbird
- For Firefox: If running a version older than 140.12.0 ESR, upgrade to Firefox ESR 140.12 or later; if running 140.x-151.x, upgrade to Firefox 152 or later
- For Thunderbird: If running a version older than 140.12.0 ESR, upgrade to Thunderbird ESR 140.12 or later; if running 140.x-151.x, upgrade to Thunderbird 152 or later
- Download the latest version from the official Mozilla website (www.mozilla.org) or use the built-in update mechanism
- Restart the application after updating to ensure the new version is fully applied
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,808.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-12310 — 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-2026-12310 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
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