CVE-2026-14899

Name of the Vulnerable Software and Affected Versions Thunderbird versions prior to 153 Thunderbird versions prior to 140.13

Description An off-by-one error exists in the code used to parse MIME headers (Multipurpose Internet Mail Extensions) for display when forwarding a message, specifically when the setting to view all headers is enabled. This flaw allows a single byte to be read from memory beyond the header buffer, which can lead to an application crash.

Recommendations Update to version 153. Update to version 140.13.