CVE-2021-38504: Debian Linux

High severity, CVSS 8.8. EPSS: 1.8% chance of exploitation in the next 30 days.

When interacting with an HTML input element's file picker dialog with webkitdirectory set, a use-after-free could have resulted, leading to memory corruption and a potentially exploitable crash. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.

Affected products

• Debian Debian Linux: version 9.0 only; version 10.0 only; version 11.0 only
• Mozilla Firefox: before 94.0 (fixed in 94.0)
• Mozilla Firefox ESR: before 91.3.0 (fixed in 91.3.0)
• Mozilla Thunderbird: before 91.3.0 (fixed in 91.3.0)

Published 2021-12-08. Last modified 2026-06-17.