CVE-2024-3863Network attack vector

Executable warning bypass via .xrm-ms downloads

Published Apr 16, 2024 · Updated Aug 22, 2025

Download protection bypass in Mozilla Firefox, Firefox ESR, and Thunderbird allows remote attackers to suppress an executable-file warning. Mozilla has not published the code-level cause; the documented failure is confined to the Windows warning path for downloaded .xrm-ms files. The condition affects Firefox before 125, Firefox ESR before 115.10, and Thunderbird before 115.10; other platforms are unaffected.

CVSS severity9.8
Critical
EPSS probability0.81%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Download protection bypass in Mozilla Firefox, Firefox ESR, and Thunderbird allows remote attackers to suppress an executable-file warning. Mozilla has not published the code-level cause; the documented failure is confined to the Windows warning path for downloaded .xrm-ms files. The condition affects Firefox before 125, Firefox ESR before 115.10, and Thunderbird before 115.10; other platforms are unaffected.

The record

CVE
CVE-2024-3863
Published
Apr 16, 2024
Updated
Aug 22, 2025
Vendor
Mozilla
Product
Firefox
Classifications
CWE-434
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 16, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 22, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <125

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <125
Mozilla · Thunderbirdversion=unspecified <115.10
Mozilla · Firefox ESRversion=unspecified <115.10

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo