CVE-2026-84640: high-severity vulnerability in Mozilla Thunderbird
One byte overflow read in mail parser
Published · Updated
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21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.3%
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Affected products
Mozilla · ThunderbirdRelated CVEs — Mozilla Thunderbird
In the same product, most dangerous first.