CVE-2026-100775: Mozilla Firefox

Critical severity, CVSS 9.6. EPSS: 0.3% chance of exploitation in the next 30 days.

Sandbox escape in the Graphics 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.

Affected products

• Mozilla Firefox: from 115.0.1, before 115.42.0 (fixed in 115.42.0); from 140.0.0, before 140.17.0 (fixed in 140.17.0); from 153.0.0, before 153.4.0 (fixed in 153.4.0); from 154.0.0, before 157.0.0 (fixed in 157.0.0)
• Mozilla Thunderbird: from 140.0, before 140.17.0 (fixed in 140.17.0); from 153.0, before 153.4.0 (fixed in 153.4.0); from 154.0, before 157.0 (fixed in 157.0)

Published 2026-09-29. Last modified 2026-10-06.