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.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Alma_linux | — | Upgrade thunderbird | Aug 5, 2026 | Aug 4, 2026 |
| Debian | — | Upgrade thunderbird | Aug 9, 2026 | Aug 9, 2026 |
| Mozilla Thunderbird | — | Upgrade to Mozilla Thunderbird version 140.13Upgrade to the latest version of Mozilla Thunderbird | Jul 21, 2026 | Jul 21, 2026 |
| Redhat_linux | — | Upgrade thunderbirdUpgrade thunderbird-debugsourceUpgrade thunderbird-debuginfoNo solution exists | Jul 29, 2026 | Jul 22, 2026 |
| Rocky_linux | — | Upgrade thunderbird-debugsourceUpgrade thunderbirdUpgrade thunderbird-debuginfo | Aug 7, 2026 | Aug 6, 2026 |
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