dbcve.org
FirefoxWeb browser · Mozilla

CVE-2026-16357

CRITICAL · 9.8 CVSS v3.1 Published 2026-07-21
Fix available
A fix is available. Upgrade to 115.38.0 / 140.13.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 4 weeks old

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 · unedited
Incorrect boundary conditions in the Graphics component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

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 confidence

A boundary condition error in the Firefox/Thunderbird Graphics component allows incorrect memory access during rendering operations. The flaw likely permits out-of-bounds read/write operations that can be triggered by specially crafted graphical content, potentially enabling remote code execution.

MitigationUpdate vulnerable installations to Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, or Thunderbird 140.13. Organizations should prioritize automated patch deployment to address this critical-severity flaw.

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
Affected:< 115.38.0< 153.0.0>= 128.1.0, < 140.13.0
ThunderbirdApplication
Affected:< 140.13.0>= 141.0, < 153.0

CVSS 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
High
Availability
High

CVSS:3.1/AV:N/AC:L/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Mozilla Firefox version
    In Firefox, navigate to Help > About Firefox, or enter 'about:support' in the address bar. The version number is displayed at the top of the page next to 'Version'.
    Affected if Version is less than 115.38.0, OR less than 153.0.0, OR between 128.1.0 and 140.13.0 (excluding 140.13.0)
  2. Identify installed Thunderbird version
    In Thunderbird, navigate to Help > About Thunderbird, or enter 'about:support' in the address bar. The version number is displayed at the top of the page next to 'Version'.
    Affected if Version is less than 140.13.0, OR between 141.0.0 and 153.0.0 (excluding 153.0)
  3. Confirm product type
    Review whether the detected application is Firefox (web browser) or Thunderbird (email client). Both share the Graphics component and are affected by this CVE.
    Affected if Either product is installed with a version matching the affected ranges above

You are affected if either Firefox or Thunderbird is installed with a version falling within the vulnerable ranges (less than 115.38.0, less than 140.13.0, less than 153.0, or between 128.1.0-140.13.0 for Firefox; less than 140.13.0 or between 141.0-153.0 for Thunderbird).

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 115.38.0 / 140.13.0 / 153.0 or later
Fixed in 115.38.0140.13.0153.0
Interim mitigation

Update vulnerable installations to Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, or Thunderbird 140.13. Organizations should prioritize automated patch deployment to address this critical-severity flaw.

Recommended fix High confidence

Firefox 153 (or ESR 115.38/140.13 depending on branch), Thunderbird 153 (or 140.13)

  1. Check current Firefox or Thunderbird version by navigating to Menu > Help > About (or typing 'about:support' in the address bar)
  2. If the installed version is earlier than Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, or Thunderbird 140.13, download the appropriate fixed version from the official Mozilla website (www.mozilla.org)
  3. Close all Firefox/Thunderbird instances completely
  4. Install the updated version by running the downloaded installer
  5. After installation, restart the application and verify the version at Menu > Help > About
Caveat Standard upgrade; ensure any compatible extensions/add-ons are updated

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
6.0 hours of engineering $1,040
Get the upgrade done

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 locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-16357 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-16357 in production — separate from our analysis above.

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.

What this is

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.

What belongs here
  • 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