CVE-2026-84639
CVSS v3
9.1
CRITICAL
EPSS Score
0.3 %
exploit probability, as of 2026-09-28
CISA KEV
No
known exploited
Exploitation
—
SSVC status
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.
Technical details
- Published
- 2026-09-01
- Last Modified
- 2026-09-02
Frequently asked questions
What is CVE-2026-84639?
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.
Is CVE-2026-84639 actively exploited?
Active exploitation of CVE-2026-84639 has not been confirmed. Its EPSS score was 0.3% on 2026-09-28, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2026-84639?
CVE-2026-84639 has a CVSS v3 base score of 9.1 (CRITICAL severity).
Is CVE-2026-84639 affecting your environment?
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