CVE-2026-8959

CRITICAL 9.6CVE-2026-8959 · Published 19/05/2026 · updated 14/10/2026

Package	Affected versions	Patched versions
firefox mozilla	`< 140.11.0< 151.0.0`	`140.11.0151.0.0`
thunderbird mozilla	`< 140.11< 151.0.0`	`140.11151.0.0`

Description

Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

References

bugzilla.mozilla.org/show_bug.cgi · Permissions Required
mozilla.org/security/advisories/mfsa2026-46 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-48 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-50 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-51 · Vendor Advisory

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