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FirefoxWeb browser · Mozilla

CVE-2025-4089

MEDIUM · 5.1 CVSS v3.1 Published 2025-04-29
Fix available
A fix is available. Upgrade to 138.0 or later.
See remediation →
56/100
Remediation priority · Elevated
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
Due to insufficient escaping of special characters in the "copy as cURL" feature, an attacker could trick a user into using this command, potentially leading to local code execution on the user's system. This vulnerability was fixed in Firefox 138 and Thunderbird 138.

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 cross-site scripting-like vulnerability exists in Firefox and Thunderbird's 'copy as cURL' feature where special characters are insufficiently escaped. An attacker who can influence the content being copied (e.g., through malicious web content) can craft a cURL command that, when executed by the user, will inject and run arbitrary local commands due to improper handling of shell metacharacters in the generated cURL string.

MitigationUpgrade to Firefox 138 or Thunderbird 138 or later. As a workaround, avoid using the 'copy as cURL' feature until the patch is applied, and carefully inspect any cURL commands before executing them.

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:< 138.0
ThunderbirdApplication
Affected:< 138.0

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
Local
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:L/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 Firefox version
    In Firefox, go to menu > Help > About Firefox, or enter 'about:support' in the address bar, or run 'firefox --version' in command line
    Affected if Version displayed is below 138.0 (e.g., 137.x or earlier)
  2. Identify installed Thunderbird version
    In Thunderbird, go to menu > Help > About Thunderbird, or run 'thunderbird --version' in command line
    Affected if Version displayed is below 138.0 (e.g., 137.x or earlier)
  3. Confirm product usage
    Determine if Firefox or Thunderbird is actively used for web browsing or email
    Affected if Either product is installed and in use
  4. Assess 'copy as cURL' feature usage
    The 'copy as cURL' feature exists in Firefox Developer Tools (Network tab) and Thunderbird. It is a built-in feature that cannot be disabled via configuration.
    Affected if User has used or may use the 'copy as cURL' feature to copy requests from web content or emails

User is affected if running Firefox or Thunderbird version below 138.0, as the vulnerable 'copy as cURL' feature is built-in and present in these versions.

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 138.0 or later
Fixed in 138.0
Interim mitigation

Upgrade to Firefox 138 or Thunderbird 138 or later. As a workaround, avoid using the 'copy as cURL' feature until the patch is applied, and carefully inspect any cURL commands before executing them.

Recommended fix High confidence

Firefox 138.0 or later / Thunderbird 138.0 or later

  1. Check your current Firefox or Thunderbird version by navigating to Help > About Firefox or Help > About Thunderbird
  2. Download and install Firefox 138.0 or later from the official Mozilla website (www.mozilla.org)
  3. Download and install Thunderbird 138.0 or later from the official Mozilla website (www.mozilla.org)
  4. Verify the update was successful by checking the version again in Help > About

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 / QA2.0 h
11.0 hours of engineering $1,930
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

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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-2025-4089 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