CVE-2026-4691

9.8 CRITICAL

Published: March 24, 2026 Modified: April 13, 2026

Description

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.

AI Explanation

Get an AI-powered plain-language explanation of this vulnerability and remediation steps.

CVSS v3.x Details

0.0 Low Medium High Critical 10.0

Vector String

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory

https://bugzilla.mozilla.org/show_bug.cgi?id=2017512

Source: security@mozilla.org

Permissions Required

https://www.mozilla.org/security/advisories/mfsa2026-20/

Source: security@mozilla.org

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026-21/

Source: security@mozilla.org

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026-22/

Source: security@mozilla.org

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026-23/

Source: security@mozilla.org

https://www.mozilla.org/security/advisories/mfsa2026-24/

Source: security@mozilla.org

6 reference(s) from NVD

Quick Stats

CVSS v3 Score

9.8 / 10.0

EPSS (Exploit Probability)

0.0%

10th percentile

Exploitation Status

Not in CISA KEV

Weaknesses (CWE)

CWE-416 CWE-416

Affected Vendors

mozilla

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