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8.1 High

CVE-2025-4091 Memory safety bugs present in Firefox 137, Thunderbird 137, Firefox ESR 128.9, and Thunderbird 128.9

Description

Memory safety bugs present in Firefox 137, Thunderbird 137, Firefox ESR 128.9, and Thunderbird 128.9. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 138, Firefox ESR 128.10, Thunderbird 138, and Thunderbird 128.10.

Affected products and versions

Product Affected versions Fixed in
Firefox 138 earliest → < 138 138
Firefox 128.10 earliest → < 128.10 128.10
Firefox ESR 128.10 earliest → < 128.10 128.10
Thunderbird 138 earliest → < 138 138
Thunderbird 128.10 earliest → < 128.10 128.10

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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