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VulnerabilityPublished Updated

CVE-2024-3863: Mozilla Firefox · Unrestricted File Upload

Affects Mozilla FirefoxSource CVE Database V5

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Not known to be exploited · CVSS 9.8 Critical.

Data as of 4 Nov 2026, 00:28 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CISA-ADPCVSS 3.19.8
EPSS
0.8% chance of exploitation in 30 days – higher than 57% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2025-08-22.

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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 16 Apr 2024

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 3 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
MozillaFirefoxAffected
  • ≥ unspecified, < 125
Fixed in–
MozillaFirefox ESRAffected
  • ≥ unspecified, < 115.10
Fixed in–
MozillaThunderbirdAffected
  • ≥ unspecified, < 115.10
Fixed in–

AI-suggested

This vulnerability has been fixed in Firefox 125, Firefox ESR 115.10, and Thunderbird 115.10. Users and administrators should update affected Mozilla products to these versions or later to mitigate the risk. No additional mitigation steps are required beyond applying the official patches.

Description

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.

References

Community reviews

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