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9.6 Critical

CVE-2026-84121 Sandbox escape due to use-after-free in the DOM: Security component

Description

Sandbox escape due to use-after-free in the DOM: Security component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

Affected products and versions

Product Affected versions Fixed in
Firefox 155 earliest → < 155 155
Firefox 153.2 earliest → < 153.2 153.2
Firefox 140.15 earliest → < 140.15 140.15
Firefox 115.40 earliest → < 115.40 115.40
Thunderbird 155 earliest → < 155 155
Thunderbird 153.2 earliest → < 153.2 153.2
Thunderbird 140.15 earliest → < 140.15 140.15

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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