CVE-2021-29945: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 1.2% chance of exploitation in the next 30 days.

The WebAssembly JIT could miscalculate the size of a return type, which could lead to a null read and result in a crash. *Note: This issue only affected x86-32 platforms. Other platforms are unaffected.*. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.

Affected products

• Mozilla Firefox: before 88.0 (fixed in 88.0)
• Mozilla Firefox ESR: before 78.10 (fixed in 78.10)
• Mozilla Thunderbird: before 78.10 (fixed in 78.10)

Published 2021-06-24. Last modified 2026-06-17.