What’s Vulnerable › Vulnerabilities

CVE-2021-38502

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-11-03 · updated 2026-06-17

Description

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 Linux: 9.0, 10.0, 11.0
• Mozilla Thunderbird: before 91.2 — fixed in 91.2

How to fix

Upgrade to a fixed version: Mozilla Thunderbird 91.2. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1733366
• https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html
• https://www.debian.org/security/2022/dsa-5034
• https://www.mozilla.org/security/advisories/mfsa2021-47/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1733366
• https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html
• https://www.debian.org/security/2022/dsa-5034
• https://www.mozilla.org/security/advisories/mfsa2021-47/

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