CVE-2026-84639

Published: Sep 1, 2026Modified: Sep 3, 2026

9.1

Vector

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

Exploitability: 3.9 / Impact: 5.2

Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Secondary)

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.

Affected (3)

Products: Mozilla: Thunderbird

Mozilla

1 product

Thunderbird

Configuration A

3 vulnerable

Vulnerable Software	Affected Versions
Mozilla Thunderbird	version < 140.15.0
Mozilla Thunderbird	141.0 ≤ version < 153.2.0
Mozilla Thunderbird	154.0 ≤ version < 155.0

Related CWEs

CWE-457

Use of Uninitialized Variable

The code uses a variable that has not been initialized, leading to unpredictable or unintended results.

References (4)

https://bugzilla.mozilla.org/show_bug.cgi?id=2061087

Source: security@mozilla.org

Permissions Required

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

Source: security@mozilla.org

Vendor Advisory

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

Source: security@mozilla.org

Vendor Advisory

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

Source: security@mozilla.org

Vendor Advisory

Timeline

No history available yet.