8.8 High

CVE-2026-117921 Use-after-free in the CSS Parsing and Computation component

Description

Use-after-free in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 detail

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

Exploitable remotely over the network, without an account and if a user takes an action; an attacker can seriously compromise confidentiality, integrity or availability.

Attack vector: Network
Attack complexity: Low
Privileges required: None
Interaction: Required
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Affected products and versions

Product	Affected versions	Fixed in
Firefox 159	earliest → < 159	159
Firefox 153.6	earliest → < 153.6	153.6
Firefox 115.44	earliest → < 115.44	115.44
Thunderbird 159	earliest → < 159	159
Thunderbird 153.6	earliest → < 153.6	153.6

References

bugzilla.mozilla.org bugzilla.mozilla.org
www.mozilla.org www.mozilla.org
www.mozilla.org www.mozilla.org
www.mozilla.org www.mozilla.org
www.mozilla.org www.mozilla.org
www.mozilla.org www.mozilla.org

Timeline

Published October 27, 2026
Last modified November 4, 2026

The 2221 CVEs of Firefox →

CVE-2026-120572 Incorrect boundary conditions in the Layout: Block and Inline component 8.8 High CVE-2026-118027 Frame poisoning in the Layout component 9.1 Critical CVE-2026-118024 Use-after-free in the Graphics: Text component 8.8 High CVE-2026-118026 Invalid pointer in the JavaScript: GC component 8.8 High

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