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9.8 Critical

CVE-2026-16387 Site isolation issue in the Networking component

Description

Site isolation issue in the Networking component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

Affected products and versions

Product Affected versions Fixed in
Firefox 153 earliest → < 153 153
Firefox 140.13 earliest → < 140.13 140.13
Thunderbird 153 earliest → < 153 153
Thunderbird 140.13 earliest → < 140.13 140.13

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