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FirefoxWeb browser · Mozilla

CVE-2024-3863

CRITICAL · 9.8 CVSS v3.1 Published 2024-04-16
Fix available
A fix is available. Upgrade to 115.10 / 115.10.0 or later.
See remediation →
100/100
Remediation priority · Urgent
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
The executable file warning was not presented when downloading .xrm-ms files. *Note: This issue only affected Windows operating systems. Other operating systems are unaffected.* This vulnerability affects Firefox < 125, Firefox ESR < 115.10, and Thunderbird < 115.10.

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

Firefox and Thunderbird failed to display the executable file warning when users downloaded .xrm-ms files on Windows systems. This allowed potentially malicious executable files to be downloaded without user warning, as .xrm-ms files (Windows Credential Manager related) were not recognized as executables requiring a warning prompt.

MitigationUpdate Firefox to version 125 or later, Firefox ESR to 115.10 or later, and Thunderbird to 115.10 or later to receive the executable warning for .xrm-ms file downloads. Until patched, avoid downloading .xrm-ms files from untrusted sources.

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:< 115.10.0< 125.0
ThunderbirdApplication
Affected:< 115.10

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 product
    Check if Firefox or Thunderbird is installed. On Windows, look in Program Files or Program Files (x86) for Mozilla Firefox or Mozilla Thunderbird folders. Alternatively, check the Windows registry under HKLM\SOFTWARE\Mozilla\Mozilla Firefox or HKLM\SOFTWARE\Mozilla\Thunderbird for the installed version.
    Affected if Neither Firefox nor Thunderbird is installed - the CVE does not apply.
  2. Check Firefox version on Windows
    Open Firefox, go to Help > About Firefox, or navigate to about:support in the address bar. The version number is displayed at the top. Alternatively, check the file properties of firefox.exe in the installation directory.
    Affected if Firefox version is less than 115.10.0 or less than 125.0 on a Windows system.
  3. Check Thunderbird version on Windows
    Open Thunderbird, go to Help > About Thunderbird, or navigate to about:support in the address bar. The version number is displayed at the top. Alternatively, check the file properties of thunderbird.exe in the installation directory.
    Affected if Thunderbird version is less than 115.10 on a Windows system.
  4. Confirm operating system is Windows
    Check the system OS by running 'winver' from the Run dialog, or checking System Properties. This vulnerability only affects Windows systems.
    Affected if Running a non-Windows operating system - the CVE does not apply.

A user is affected if they have Firefox versions below 115.10.0 or below 125.0, or Thunderbird below 115.10, and are running on Windows.

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 115.10 / 115.10.0 / 125.0 or later
Fixed in 115.10115.10.0125.0
Interim mitigation

Update Firefox to version 125 or later, Firefox ESR to 115.10 or later, and Thunderbird to 115.10 or later to receive the executable warning for .xrm-ms file downloads. Until patched, avoid downloading .xrm-ms files from untrusted sources.

Recommended fix High confidence

Firefox 125.0 (or later), Firefox ESR 115.10 (or later), Thunderbird 115.10 (or later)

  1. 1. Open Firefox or Thunderbird and navigate to Help > About Firefox/Thunderbird to check the current version
  2. 2. If the version is below 125.0 for Firefox, below 115.10 for Firefox ESR, or below 115.10 for Thunderbird, an update is required
  3. 3. Download the latest version from the official Mozilla website: https://www.mozilla.org/
  4. 4. Close all browser/application windows before installing
  5. 5. Run the installer and follow the prompts to complete the update
  6. 6. After installation, verify the version by checking Help > About again to confirm the update was successful

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
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

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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-2024-3863 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