CVE-2026-100781

CRITICAL 9.6CVE-2026-100781 · Published 29/09/2026 · updated 05/10/2026

In short

CVE-2026-100781 is a CRITICAL (CVSS 9.6) vulnerability affecting firefox (mozilla), thunderbird (mozilla).
Chance of exploitation in the next 30 days (EPSS): 0.33%, higher than 26.0% of all vulnerabilities.
Fix: update to 115.42.0, 140.17.0, 153.4.0, 157.0.0 or later.

Package	Affected versions	Patched versions
firefox mozilla	`≥ 115.1.0, < 115.42.0≥ 140.0, < 140.17.0≥ 153.0, < 153.4.0< 157.0.0`	`115.42.0140.17.0153.4.0157.0.0`
thunderbird mozilla	`≥ 140.0, < 140.17.0≥ 153.0, < 153.4.0< 157.0`	`140.17.0153.4.0157.0`

Description

Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

References

bugzilla.mozilla.org/show_bug.cgi · Permissions Required
mozilla.org/security/advisories/mfsa2026-100 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-101 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-102 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-103 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-97 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-98 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-99 · Vendor Advisory

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Package

Affected versions

Patched versions

firefox

mozilla

≥ 115.1.0, < 115.42.0≥ 140.0, < 140.17.0≥ 153.0, < 153.4.0< 157.0.0

115.42.0140.17.0153.4.0157.0.0

thunderbird

mozilla

≥ 140.0, < 140.17.0≥ 153.0, < 153.4.0< 157.0

140.17.0153.4.0157.0

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