CVE-2026-84641

high

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.

References

https://www.mozilla.org/security/advisories/mfsa2026-88/

https://www.mozilla.org/security/advisories/mfsa2026-87/

https://www.mozilla.org/security/advisories/mfsa2026-86/

https://bugzilla.mozilla.org/show_bug.cgi?id=2057805

Details

Source: Mitre, NVD

Published: 2026-09-01

Updated: 2026-09-02

Risk Information

CVSS v2

Base Score: 5

Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:N/A:N

Severity: Medium

CVSS v3

Base Score: 7.5

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

Severity: High

EPSS

EPSS: 0.0015