CVE-2026-84639

critical · 9.1

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.

9.1

CVSS

0.3%

EPSS (exploit prob.)

25th

EPSS percentile

2026-09-01

Published

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Weaknesses

CWE-457

Affected products

Vendor	Product	Affected versions
mozilla	thunderbird	< 140.15.0
mozilla	thunderbird	>= 141.0, < 153.2.0
mozilla	thunderbird	>= 154.0, < 155.0

Check a specific version with /api/v1/cve/match.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2061087
https://www.mozilla.org/security/advisories/mfsa2026-86/
https://www.mozilla.org/security/advisories/mfsa2026-87/
https://www.mozilla.org/security/advisories/mfsa2026-88/

Query this programmatically:

curl https://evil-db.io/api/v1/cve/CVE-2026-84639