Use-After-Free Vulnerability in Firefox by Mozilla
CVE-2026-100815

8.8HIGH

Key Information:

Vendor

Mozilla
Status
Firefox
Thunderbird
Vendor
CVE Published:
29 September 2026

What is CVE-2026-100815?

A use-after-free vulnerability has been identified in the CSS Parsing and Computation component of Mozilla Firefox. This flaw can potentially allow attackers to execute arbitrary code under certain conditions, creating risks for users who have not updated to the patched versions. The vulnerability was addressed with updates in Firefox ESR 153.4 and Firefox 157, highlighting the importance of regular software maintenance and prompt installation of security updates to safeguard against exploitation.

Affected Version(s)

Firefox 153.4

Firefox 157

Thunderbird 153.4

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2068404
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
.