dbcve.org
FirefoxWeb browser · Mozilla

CVE-2025-4919

HIGH · 8.8 CVSS v3.1 Published 2025-05-17
Fix available
A fix is available. Upgrade to 115.23.1 / 128.10.1 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges

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
An attacker was able to perform an out-of-bounds read or write on a JavaScript object by confusing array index sizes. This vulnerability was fixed in Firefox 138.0.4, Firefox ESR 128.10.1, Firefox ESR 115.23.1, Thunderbird 128.10.2, and Thunderbird 138.0.2.

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 confidence

An out-of-bounds memory access vulnerability in Firefox and Thunderbird's JavaScript engine allows attackers to read or write beyond array boundaries by confusing array index sizes, potentially leading to memory corruption and arbitrary code execution.

MitigationUpdate to Firefox 138.0.4, Firefox ESR 128.10.1, Firefox ESR 115.23.1, Thunderbird 128.10.2, Thunderbird 138.0.2 or later versions to patch the vulnerability.

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:< 115.23.1< 138.0.4>= 116.0, < 128.10.1
ThunderbirdApplication
Affected:< 128.10.2>= 138.0, < 138.0.2

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
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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 products
    Run 'firefox --version' for Firefox or 'thunderbird --version' for Thunderbird. On Windows, check Help > About in the application menu.
    Affected if Either Firefox or Thunderbird is installed and the version matches the affected ranges below.
  2. Check Firefox version against affected ranges
    Compare the installed Firefox version to: < 115.23.1, < 138.0.4, or >= 116.0 but < 128.10.1. Versions 115.23.1+, 128.10.1+, and 138.0.4+ are not affected.
    Affected if Firefox version is less than 115.23.1, less than 138.0.4, or between 116.0 and 128.10.0 (inclusive).
  3. Check Thunderbird version against affected ranges
    Compare the installed Thunderbird version to: < 128.10.2 or >= 138.0 but < 138.0.2. Versions 128.10.2+ and 138.0.2+ are not affected.
    Affected if Thunderbird version is less than 128.10.2, or between 138.0.0 and 138.0.1 (inclusive).

You are affected if either Firefox or Thunderbird is installed with a version that falls within the affected ranges listed above.

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 115.23.1 / 128.10.1 / 128.10.2 or later
Fixed in 115.23.1128.10.1128.10.2
Interim mitigation

Update to Firefox 138.0.4, Firefox ESR 128.10.1, Firefox ESR 115.23.1, Thunderbird 128.10.2, Thunderbird 138.0.2 or later versions to patch the vulnerability.

Recommended fix High confidence

Firefox 115.23.1, Firefox ESR 128.10.1, Firefox 138.0.4, Thunderbird 128.10.2, or Thunderbird 138.0.2 (depending on your release channel)

  1. Identify the currently installed Firefox or Thunderbird version from the Help > About menu or by running 'firefox --version' or 'thunderbird --version'
  2. For Firefox 115.x users: Upgrade to Firefox 115.23.1 or later
  3. For Firefox 116.x through 127.x users: Upgrade to Firefox 128.10.1 (ESR) or the latest available release
  4. For Firefox 128.x ESR users: Upgrade to Firefox ESR 128.10.1 or later
  5. For Firefox 138.x users before 138.0.4: Upgrade to Firefox 138.0.4 or later
  6. For Thunderbird users before 128.10.2: Upgrade to Thunderbird 128.10.2 or later
  7. For Thunderbird 138.x users before 138.0.2: Upgrade to Thunderbird 138.0.2 or later
  8. After upgrading, verify the version by checking Help > About to confirm the fix is applied
Caveat Standard Mozilla release upgrades typically have minimal breaking changes; however, some legacy add-ons or extensions may be incompatible with newer versions

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
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,424.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2025-4919 — 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-2025-4919 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