CVE-2026-100817: Mozilla Firefox

Medium severity, CVSS 5.4. EPSS: 0.2% chance of exploitation in the next 30 days.

Other issue in the JavaScript: WebAssembly component. This vulnerability was fixed in Thunderbird 157 and Firefox 157.

Affected products

• Mozilla Firefox: before 157.0.0 (fixed in 157.0.0)
• Mozilla Thunderbird: before 157.0 (fixed in 157.0)

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