CVE-2026-100815 Firefox - Use After Free

Firefox ESR < 153.4 and Firefox < 157 contain a use-after-free vulnerability caused by improper memory handling in the CSS Parsing and Computation component, letting attackers cause memory corruption or remote code execution, exploit requires crafted content.

CVSS base score 8.8 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.23% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Use After Free
Impact
Remote Code Execution, Denial Of Service
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Published
29 September 2026
Updated
15 October 2026
Weakness
CWE-416

Vendor fix

Update to Firefox ESR 153.4, Firefox 157 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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