Security Advisory
CVE-2026-14899
7.5
HIGH
Vulnerability Description
The code to parse MIME headers for display when forwarding a message (if the setting to view all headers was enabled) had an off-by-one error, allowing a single byte to be read from the memory after the buffer for the headers, and potentially crashing Thunderbird. This vulnerability was fixed in Thunderbird 153 and Thunderbird 140.13.
Published Date
July 22, 2026
Official Source
NIST NVD Advisory