CVE-2021-38500: Debian Linux

High severity, CVSS 8.8. EPSS: 1.3% chance of exploitation in the next 30 days.

Mozilla developers reported memory safety bugs present in Firefox 92 and Firefox ESR 91.1. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Thunderbird < 78.15, Thunderbird < 91.2, Firefox ESR < 91.2, Firefox ESR < 78.15, and Firefox < 93.

Affected products

• Debian Debian Linux: version 9.0 only; version 10.0 only; version 11.0 only
• Mozilla Firefox: before 93.0 (fixed in 93.0); from 91.0, before 91.2 (fixed in 91.2)
• Mozilla Firefox ESR: before 78.15 (fixed in 78.15)
• Mozilla Thunderbird: before 78.15 (fixed in 78.15); from 91.0, before 91.2 (fixed in 91.2)

Published 2021-11-03. Last modified 2026-06-17.