CVE-2021-38502: Debian Linux

Medium severity, CVSS 5.9. EPSS: 1.1% chance of exploitation in the next 30 days.

Thunderbird ignored the configuration to require STARTTLS security for an SMTP connection. A MITM could perform a downgrade attack to intercept transmitted messages, or could take control of the authenticated session to execute SMTP commands chosen by the MITM. If an unprotected authentication method was configured, the MITM could obtain the authentication credentials, too. This vulnerability affects Thunderbird < 91.2.

Affected products

• Debian Debian Linux: version 9.0 only; version 10.0 only; version 11.0 only
• Mozilla Thunderbird: before 91.2 (fixed in 91.2)

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