CVE-2021-38502 Security feature bypass in Thunderbird

What is CVE-2021-38502?

CVE-2021-38502 is a medium-severity vulnerability in Debian Debian Linux, published on 3 Nov 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Which versions are affected by CVE-2021-38502?

It affects 2 products.

Products include Debian Debian Linux, Mozilla Thunderbird.

How do I fix CVE-2021-38502?

Upgrade to a fixed version.

Is CVE-2021-38502 being exploited?

There is no known exploitation of CVE-2021-38502 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

• CVE-2015-3306 ProFTPD Improper Access Control Exploited Critical 10.0
• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2021-38502, GHSA-wf24-4m95-7wjm, UBUNTU-CVE-2021-38502.