CVE-2026-84641

Information disclosure due to malicious IMAP server response

State: Published
Severity: 7.5 High
Published: Sep 1, 2026
Updated: Sep 2, 2026
Reserved: Sep 1, 2026

Description

A malicious IMAP server can trigger use-after-free and heap-memory disclosure by sending a crafted ID response. Heap contents can ultimately be persisted to prefs.js. This vulnerability was fixed in Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

Scores

CVSS	Score	Vector	Source
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N	CISA-ADP

Weaknesses

CWE-416 Use After Free

Affected Products

Product	Versions
ThunderbirdMozilla	140.15 through 140.Not affected 153.2 through 153.Not affected 155 and laterNot affected

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2057805
https://www.mozilla.org/security/advisories/mfsa2026-86/
https://www.mozilla.org/security/advisories/mfsa2026-87/
https://www.mozilla.org/security/advisories/mfsa2026-88/

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