CVE-2024-3855: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

In certain cases the JIT incorrectly optimized MSubstr operations, which led to out-of-bounds reads. This vulnerability affects Firefox < 125.

Affected products

• Mozilla Firefox: before 125.0 (fixed in 125.0)

Published 2024-04-16. Last modified 2026-06-17.