Use-After-Free Vulnerability in Firefox by Mozilla
CVE-2026-100831

8.8HIGH

Key Information:

Vendor

Mozilla
Status
Firefox
Thunderbird
Vendor
CVE Published:
29 September 2026

What is CVE-2026-100831?

A use-after-free vulnerability was identified in the DOM handling of UI Events and Focus Management in Firefox. This flaw may enable attackers to exploit freed memory, potentially leading to arbitrary code execution, data corruption, or application crashes. The issue has been addressed in the latest versions of Firefox ESR and standard Firefox builds, ensuring enhanced protection against such memory-related vulnerabilities.

Affected Version(s)

Firefox 153.4

Firefox 157

Thunderbird 153.4

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2067172
https://www.mozilla.org/security/advisories/mfsa2026-100/
https://www.mozilla.org/security/advisories/mfsa2026-101/

CVSS V3.1

Score:
8.8
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Mozilla
.