CVE-2026-4691

CWE-416 — Use After FreeCWE-82513 documents9 sources
Severity
9.8CRITICAL
EPSS
0.0%
top 89.80%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
3
Mozilla FirefoxMozilla Firefox ESRMozilla Thunderbird
Timeline
PublishedMar 24

Description

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

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitability: 3.9 | Impact: 5.9

Affected Packages6 packages

▶CVEListV5mozilla/firefoxunspecified — 149
▶NVDmozilla/firefox128.0 — 140.9.0+2
▶CVEListV5mozilla/firefox_esrunspecified — 115.34+1
▶Debianfirefox-esr< 140.9.0esr-1~deb11u1+3
▶CVEListV5mozilla/thunderbirdunspecified — 149+1

🔴Vulnerability Details

3
OSV
CVE-2026-4691: Use-after-free in the CSS Parsing and Computation component↗2026-03-24
▶
GHSA
GHSA-h895-88fj-h89r: Use-after-free in the CSS Parsing and Computation component↗2026-03-24
▶
CVEList
Use-after-free in the CSS Parsing and Computation component↗2026-03-24
▶

📋Vendor Advisories

7
Red Hat
firefox: thunderbird: Use-after-free in the CSS Parsing and Computation component↗2026-03-24
▶
Debian
CVE-2026-4691: firefox - Use-after-free in the CSS Parsing and Computation component. This vulnerability ...↗2026
▶
Mozilla
Mozilla Foundation Security Advisory 2026-23: CVE-2026-4691↗
▶
Mozilla
Mozilla Foundation Security Advisory 2026-20: CVE-2026-4691↗
▶
Mozilla
Mozilla Foundation Security Advisory 2026-24: CVE-2026-4691↗
▶

🕵️Threat Intelligence

1
Wiz
CVE-2026-4691 Impact, Exploitability, and Mitigation Steps | Wiz↗
▶

💬Community

1
Bugzilla
CVE-2026-4691 firefox: thunderbird: Use-after-free in the CSS Parsing and Computation component↗2026-03-24
▶
CVE-2026-4691 (CRITICAL CVSS 9.8) | Use-after-free in the CSS Parsing a | cvebase.io