CVE-2026-4691

Use-after-free in the CSS Parsing and Computation component

Critical · published March 24, 2026

CVSS v3.1
9.8
EPSS
1%
Percentile
42.1
In the wild
Unconfirmed
What it is

Use-after-free in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

The record
Technical detail
CVSS v3.1
9.8 · CRITICAL
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.00502 · 42.1th percentile
Published
2026-03-24T12:30Z
EPSS history
Timeline
  • 24 MAR 12:30Z
    Use-after-free in the CSS Parsing and Computation component
    cvelistv5