FirefoxWeb browser · Mozilla
CVE-2026-4708
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 · uneditedIncorrect boundary conditions in the Graphics component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
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 boundary condition vulnerability exists in the Graphics component of Mozilla Firefox and Thunderbird. Incorrect boundary conditions typically indicate improper bounds checking that could allow out-of-bounds memory access, potentially leading to denial of service or memory corruption. This issue was patched in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
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
< 140.9.0< 149.0CVSS 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.
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Identify installed Firefox versionIn Firefox, go to Menu > Help > About Firefox, or enter 'about:support' in the address bar. The version number is displayed at the top.Affected if The displayed version is less than 149.0 (for regular Firefox) or less than 140.9.0 (for Firefox ESR)
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Identify installed Thunderbird versionIn Thunderbird, go to Menu > Help > About Thunderbird, or enter 'about:support' in the address bar. The version number is displayed at the top.Affected if The displayed version is less than 149.0 (for regular Thunderbird) or less than 140.9.0 (for Thunderbird ESR)
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Confirm whether using ESR variantCheck the version string: if it contains 'ESR' (for example, '140.8.0 ESR'), it is an Extended Support Release. Otherwise, it is a regular release.Affected if Using Firefox ESR below 140.9.0 or Thunderbird ESR below 140.9.0, or using regular Firefox below 149.0 or regular Thunderbird below 149.0
The environment is affected if any installed Firefox or Thunderbird version is below the patched releases: Firefox < 149.0, Firefox ESR < 140.9.0, Thunderbird < 149.0, or Thunderbird ESR < 140.9.0.
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 · scoped140.9.0149.0
Update affected installations to Firefox 149 or later, Firefox ESR 140.9 or later, Thunderbird 149 or later, or Thunderbird 140.9 or later.
Firefox 149 (regular) or Firefox ESR 140.9 (ESR)
- Check current Firefox version by navigating to Menu > Help > About Firefox
- If using regular Firefox: Download and install Firefox 149 or later from the official Mozilla website
- If using Firefox ESR: Download and install Firefox ESR 140.9 or later
- Restart Firefox after the update completes
- Verify the update was successful by checking Menu > Help > About Firefox shows version 149 or ESR 140.9
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-2026-4708 — 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-2026-4708 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