9.1
Critical
CVE-2026-84639 Triggering an error condition in certain MIME bodies would cause uninitialized memory to be used
Description
Triggering an error condition in certain MIME bodies would cause uninitialized memory to be used. 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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