CVE-2026-84640

Name of the Vulnerable Software and Affected Versions Thunderbird versions prior to 140.15 Thunderbird versions prior to 153.2 Thunderbird versions prior to 155

Description A maliciously constructed mail header can cause a one byte read past the end of a buffer, which is a memory safety issue where the program reads data outside the intended boundary of a memory buffer.

Recommendations Update to version 140.15 Update to version 153.2 Update to version 155