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FirefoxWeb browser · Mozilla

CVE-2025-0242

MEDIUM · 6.5 CVSS v3.1 Published 2025-01-07
Fix available
A fix is available. Upgrade to 128.6.0 / 134.0 or later.
See remediation →
74/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

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
Memory safety bugs present in Firefox 133, Thunderbird 133, Firefox ESR 115.18, Firefox ESR 128.5, Thunderbird 115.18, and Thunderbird 128.5. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Firefox ESR 115.19, Thunderbird 134, and Thunderbird 128.6.

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

Memory safety bugs in Firefox 133 and Thunderbird 133 (and ESR variants) allow memory corruption that could potentially be exploited for arbitrary code execution. This is a class of memory safety issues rather than a single specific vulnerability.

MitigationUpdate affected installations to Firefox 134, Firefox ESR 128.6/115.19, Thunderbird 134, or Thunderbird 128.6 to receive the fixed versions.

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:<= 115.19.0< 134.0>= 116.0, < 128.6.0
ThunderbirdApplication
Affected:< 128.6.0>= 129.0, < 134.0

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
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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 checks

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

  1. Identify installed Mozilla Firefox version
    Run 'firefox --version' on Linux/macOS, or on Windows open Firefox and go to Help > About Firefox to view the version number
    Affected if Version is 133.x or below, or ESR version is below 115.19.1 or below 128.6.0 (specifically: <=115.19.0; >=116.0 and <128.6.0; or >=129.0 and <134.0)
  2. Identify installed Thunderbird version
    Run 'thunderbird --version' on Linux/macOS, or on Windows open Thunderbird and go to Help > About Thunderbird to view the version number
    Affected if Version is any 133.x through 129.x, or ESR version is below 128.6.0 (specifically: >=129.0 and <134.0, or <128.6.0)

A user is affected if either Firefox or Thunderbird is installed and the displayed version is lower than 134.0 (or lower than 128.6.0 for ESR releases, or lower than 115.19.1 for Firefox ESR 115.x)

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 128.6.0 / 134.0 or later
Fixed in 128.6.0134.0
Interim mitigation

Update affected installations to Firefox 134, Firefox ESR 128.6/115.19, Thunderbird 134, or Thunderbird 128.6 to receive the fixed versions.

Recommended fix High confidence

Firefox 134.0+ / Firefox ESR 128.6.0+ / Firefox ESR 115.19+ / Thunderbird 134.0+ / Thunderbird 128.6.0+

  1. Check current Firefox or Thunderbird version by navigating to Help > About (Firefox) or Help > About Thunderbird
  2. Download Firefox 134.0 or later from www.mozilla.org/firefox/download
  3. Download Thunderbird 134.0 or later from www.mozilla.org/thunderbird/download
  4. Alternatively, for ESR users: Download Firefox ESR 128.6.0 or later, or Firefox ESR 115.19 or later
  5. Alternatively, for Thunderbird ESR users: Download Thunderbird 128.6.0 or later
  6. Install the downloaded version over the existing installation
  7. Restart the application after installation

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

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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-2025-0242 in production — separate from our analysis above.

No notes yet

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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