CVE-2025-5986

Severity CVSS v4.0:

Pending analysis

Type:

Unavailable / Other

Publication date:

11/06/2025

Last modified:

13/04/2026

Description

A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to the user&#39;s desktop or home directory without prompting, even if auto-saving is disabled. This behavior can be abused to fill the disk with garbage data (e.g. using /dev/urandom on Linux) or to leak Windows credentials via SMB links when the email is viewed in HTML mode. While user interaction is required to download the .pdf file, visual obfuscation can conceal the download trigger. Viewing the email in HTML mode is enough to load external content. This vulnerability was fixed in Thunderbird 128.11.1 and Thunderbird 139.0.2.

Impact

Vector 3.x

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

Base Score: 6.50 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

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

Base Score 3.x

6.50

Severity 3.x

MEDIUM

Vulnerable products and versions

CPE	From	Up to
cpe:2.3:a:mozilla:thunderbird:::::-:::*		128.11.1 (excluding)
cpe:2.3:a:mozilla:thunderbird:::::-:::*	135.0 (including)	139.0.2 (excluding)

To consult the complete list of CPE names with products and versions, see this page

CVE-2025-5986

Description

Impact

Vulnerable products and versions

References to Advisories, Solutions, and Tools