CVE-2024-9394: Mozilla Firefox

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

An attacker could, via a specially crafted multipart response, execute arbitrary JavaScript under the `resource://devtools` origin. This could allow them to access cross-origin JSON content. This access is limited to "same site" documents by the Site Isolation feature on desktop clients, but full cross-origin access is possible on Android versions. This vulnerability affects Firefox < 131, Firefox ESR < 128.3, Firefox ESR < 115.16, Thunderbird < 128.3, and Thunderbird < 131.

Affected products

• Mozilla Firefox: before 131.0 (fixed in 131.0)
• Mozilla Firefox ESR: before 115.16.0 (fixed in 115.16.0); from 116.0, before 128.3.0 (fixed in 128.3.0)
• Mozilla Thunderbird: before 128.3 (fixed in 128.3); version 129.0 only

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