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9.1 Critical

CVE-2026-74986 Site isolation issue in the CSS Parsing and Computation component

Description

Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.

Affected products and versions

Product Affected versions Fixed in
Firefox 154 earliest → < 154 154
Firefox 153.1 earliest → < 153.1 153.1
Thunderbird 154 earliest → < 154 154
Thunderbird 153.1 earliest → < 153.1 153.1

Other CVEs of Firefox

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-2026-118026 Invalid pointer in the JavaScript: GC component 8.8 High CVE-2026-118025 Other issue in the SVG component 8.8 High
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