CVE-2025-0240: Mozilla Firefox

Medium severity, CVSS 4.0. EPSS: 0.7% chance of exploitation in the next 30 days.

Parsing a JavaScript module as JSON could, under some circumstances, cause cross-compartment access, which may result in a use-after-free. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.

Affected products

• Mozilla Firefox: before 128.6.0 (fixed in 128.6.0); before 134.0 (fixed in 134.0)
• Mozilla Thunderbird: before 128.6.0 (fixed in 128.6.0); from 129.0, before 134.0 (fixed in 134.0)

Published 2025-01-07. Last modified 2026-10-05.