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CVE-2026-84640highCWE-126

One byte overflow read in mail parser

21Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 7.5epss 0.3%
exploitation probability
0.3%top 82% of all CVEs
observed exploitation
nono source reports it
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 · Thunderbird