CVE-2024-9399: Mozilla Firefox

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

A website configured to initiate a specially crafted WebTransport session could crash the Firefox process leading to a denial of service condition. This vulnerability affects Firefox < 131, Firefox ESR < 128.3, Thunderbird < 128.3, and Thunderbird < 131.

Affected products

• Mozilla Firefox: before 128.3.0 (fixed in 128.3.0); from 129.0, before 131.0 (fixed in 131.0)
• Mozilla Thunderbird: before 128.3.0 (fixed in 128.3.0); from 129.0, before 131.0 (fixed in 131.0)

Published 2024-10-01. Last modified 2026-06-17.