CVE-2026-14899

Severity CVSS v4.0:

Pending analysis

Type:

Unavailable / Other

Publication date:

22/07/2026

Last modified:

27/07/2026

Description

The code to parse MIME headers for display when forwarding a message (if the setting to view all headers was enabled) had an off-by-one error, allowing a single byte to be read from the memory after the buffer for the headers, and potentially crashing Thunderbird. This vulnerability was fixed in Thunderbird 153 and Thunderbird 140.13.

Impact

Vector 3.x

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N CVSS v3.1 Severity and Metrics:

Base Score: 7.50 HIGH
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): High
Integrity (I): None
Availability (A): None

Base Score 3.x

7.50

Severity 3.x

HIGH

References to Advisories, Solutions, and Tools

https://bugzilla.mozilla.org/show_bug.cgi?id=2046137
https://www.mozilla.org/security/advisories/mfsa2026-71/
https://www.mozilla.org/security/advisories/mfsa2026-72/