CVE-2026-84640
High
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.
SeverityHigh
CVSS7.5
Exploit probability—
Product
Mozilla Thunderbird
PublishedSep 1, 2026
First seenSep 1, 2026
Weakness typeCWE-126CWE-126
How to fix
Update
- mozilla thunderbird140.15.0, 153.2.0, 155.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla thunderbird | v < 140.15.0, 141.0 ≤ v < 153.2.0, 154.0 ≤ v < 155.0 | 140.15.0, 153.2.0, 155.0 |
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