CVE-2026-14899

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.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=2046137
• https://www.mozilla.org/security/advisories/mfsa2026-71/
• https://www.mozilla.org/security/advisories/mfsa2026-72/