7.5
High
CVE-2026-84640 A maliciously constructed mail header could lead to a one byte read past the end of a buffer
Description
A maliciously constructed mail header could lead to a one byte read past the end of a buffer. This vulnerability was fixed in Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Affected products and versions
| Product | Affected versions | Fixed in |
|---|---|---|
| Thunderbird 155 | earliest → < 155 | 155 |
| Thunderbird 153.2 | earliest → < 153.2 | 153.2 |
| Thunderbird 140.15 | earliest → < 140.15 | 140.15 |
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