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FirefoxWeb browser · Mozilla

CVE-2025-0238

MEDIUM · 5.3 CVSS v3.1 Published 2025-01-07
Fix available
A fix is available. Upgrade to 115.19.0 / 128.6 or later.
See remediation →
62/100
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
Assuming a controlled failed memory allocation, an attacker could have caused a use-after-free, leading to a potentially exploitable crash. 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 · moderate confidence

A use-after-free vulnerability in Firefox and Thunderbird where an attacker can trigger a controlled failed memory allocation, causing the application to use memory that has already been freed. This can lead to a potentially exploitable crash.

MitigationUpdate to Firefox 134, Firefox ESR 128.6/115.19, Thunderbird 134/128.6 or later to remediate this 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:< 115.19.0< 134.0>= 116.0, < 128.6.0
ThunderbirdApplication
Affected:< 128.6>= 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
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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. Check installed Firefox version on Windows
    Open Firefox, click Help > About Firefox, or go to about:support in the address bar. The version number is displayed at the top of the page.
    Affected if The version shown is earlier than 115.19.0, or earlier than 128.6.0 (for versions 116.0-127.x), or earlier than 134.0 (for versions 128.0-133.x).
  2. Check installed Firefox version on macOS
    Open Firefox, click Firefox from the menu bar, then select About Firefox. The version number appears in the dialog.
    Affected if The version shown is earlier than 115.19.0, or earlier than 128.6.0 (for versions 116.0-127.x), or earlier than 134.0 (for versions 128.0-133.x).
  3. Check installed Firefox version on Linux
    Open a terminal and run: firefox --version
    Affected if The version output is earlier than 115.19.0, or earlier than 128.6.0 (for versions 116.0-127.x), or earlier than 134.0 (for versions 128.0-133.x).
  4. Check installed Thunderbird version on Windows
    Open Thunderbird, click Help > About Thunderbird. The version number is displayed in the dialog.
    Affected if The version shown is earlier than 128.6 (for versions 129.0-133.x), or earlier than 134.0 (for versions earlier than 129.0).
  5. Check installed Thunderbird version on macOS or Linux
    On macOS: Open Thunderbird, click Thunderbird from menu, select About Thunderbird. On Linux: Open terminal and run: thunderbird --version
    Affected if The version shown is earlier than 128.6 (for versions 129.0-133.x), or earlier than 134.0 (for versions earlier than 129.0).

Your environment is affected if any installed Firefox version is below 115.19.0, below 128.6.0 (for 116.0-127.x range), or below 134.0 (for 128.0-133.x range), OR any installed Thunderbird version is below 128.6 (for 129.0-133.x range) or below 134.0 (for versions before 129.0).

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 115.19.0 / 128.6 / 128.6.0 or later
Fixed in 115.19.0128.6128.6.0
Interim mitigation

Update to Firefox 134, Firefox ESR 128.6/115.19, Thunderbird 134/128.6 or later to remediate this vulnerability.

Recommended fix High confidence

Firefox 134.0 / Firefox ESR 128.6.0 / Firefox ESR 115.19.0 / Thunderbird 134.0 / Thunderbird 128.6.0

  1. Check current Firefox or Thunderbird version via Help > About (or running 'firefox --version' / 'thunderbird --version' in terminal)
  2. For Firefox stable users: upgrade to Firefox 134.0 or later
  3. For Firefox ESR users: upgrade to Firefox ESR 128.6.0 or later (or Firefox ESR 115.19.0 or later for older ESR line)
  4. For Thunderbird users: upgrade to Thunderbird 128.6.0 or later (or Thunderbird 134.0 for stable line)
  5. Download from official Mozilla releases at https://www.mozilla.org/ or use system package manager
  6. Restart the application after upgrade
Caveat Major version upgrades may affect extension compatibility; review add-ons after upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2025-0238 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