CVE-2026-4691

Published: Mar 24, 2026Modified: Jun 17, 2026

9.8

Vector

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

Exploitability: 3.9 / Impact: 5.9

Source: NVD

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.

Affected (3)

Products: Mozilla: Firefox

Mozilla

1 product

Firefox

Configuration A

3 vulnerable

Vulnerable Software	Affected Versions
Mozilla Firefox	Before 149.0
Mozilla Firefox	Before 115.34.0
Mozilla Firefox	From 128.0 to 140.9.0

Related CWEs

CWE-416

Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

References (6)

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

Timeline

No history available yet.