CVE-2021-29982: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 1.1% chance of exploitation in the next 30 days.

Due to incorrect JIT optimization, we incorrectly interpreted data from the wrong type of object, resulting in the potential leak of a single bit of memory. This vulnerability affects Firefox < 91 and Thunderbird < 91.

Affected products

• Mozilla Firefox: before 91.0 (fixed in 91.0)
• Mozilla Thunderbird: before 91.0 (fixed in 91.0)

Published 2021-08-17. Last modified 2026-06-17.