CVE-2021-29955: Mozilla Firefox

Medium severity, CVSS 5.3. EPSS: 1.5% chance of exploitation in the next 30 days.

A transient execution vulnerability, named Floating Point Value Injection (FPVI) allowed an attacker to leak arbitrary memory addresses and may have also enabled JIT type confusion attacks. (A related vulnerability, Speculative Code Store Bypass (SCSB), did not affect Firefox.). This vulnerability affects Firefox ESR < 78.9 and Firefox < 87.

Affected products

• Mozilla Firefox: before 87.0 (fixed in 87.0)
• Mozilla Firefox ESR: before 78.9 (fixed in 78.9)

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