FirefoxWeb browser · Mozilla
CVE-2025-4093
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 present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.10 and Thunderbird 128.10.
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 · high confidenceMemory safety vulnerability in Firefox ESR 128.9 and Thunderbird 128.9 that demonstrated memory corruption. The bug could potentially be exploited with sufficient effort to achieve arbitrary code execution.
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
< 128.10< 128.10.0CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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 Mozilla productOpen the application and check Help > About, or look for Firefox or Thunderbird in your installed programs listAffected if Either Firefox ESR or Thunderbird is installed
-
Check Firefox versionFor Firefox: Type 'about:support' in the address bar and look at the 'Version' field, or run 'firefox --version' from command lineAffected if Version is below 128.10 (e.g., 128.9, 128.8, etc.)
-
Check Thunderbird versionFor Thunderbird: Type 'about:support' in the address bar and look at the 'Version' field, or run 'thunderbird --version' from command lineAffected if Version is below 128.10.0 (e.g., 128.9.0, 128.8.0, etc.)
-
Confirm release channel for Firefox ESRIn Firefox, go to Help > About Firefox - ESR versions will display 'ESR' in the version string (e.g., '128.9esr')Affected if Running Firefox ESR 128.9 or earlier (any ESR version below 128.10)
You are affected if either Mozilla Firefox (any channel) below version 128.10 or Thunderbird below version 128.10.0 is installed and running.
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 · scoped128.10128.10.0
Update immediately to Firefox ESR 128.10, Thunderbird 128.10, or later versions to remediate this memory corruption vulnerability.
Firefox ESR 128.10 or Thunderbird 128.10
- Check current Firefox or Thunderbird version via Help > About
- Download Firefox ESR 128.10 or Thunderbird 128.10 from the official Mozilla website (www.mozilla.org)
- Install the downloaded update following the standard upgrade process
- Restart the application to complete the update
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 h
- Implementation2.0 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 $1,664.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-4093 — 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-2025-4093 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