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CVE-2026-84639criticalCWE-457

Uninitialized memory in MIME parsing

28Vexday Risk Score

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

ssvc Trackcvss 9.1epss 0.3%
exploitation probability
0.3%top 74% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Affected products
Mozilla · Thunderbird