A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to the user'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 affects Thunderbird < 128.11.1 and Thunderbird < 139.0.2.
History

Thu, 12 Jun 2025 15:15:00 +0000

Type Values Removed Values Added
Title thunderbird: Unsolicited File Download, Disk Space Exhaustion, and Credential Leakage via mailbox:/// Links
Weaknesses CWE-400
References
Metrics threat_severity

None

threat_severity

Important


Wed, 11 Jun 2025 14:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-451
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 11 Jun 2025 12:15:00 +0000

Type Values Removed Values Added
Description A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to the user'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 affects Thunderbird < 128.11.1 and Thunderbird < 139.0.2.
References

cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published: 2025-06-11T12:07:50.430Z

Updated: 2025-06-11T13:20:28.401Z

Reserved: 2025-06-10T20:07:11.178Z

Link: CVE-2025-5986

cve-icon Vulnrichment

Updated: 2025-06-11T13:16:47.881Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2025-06-11T12:15:29.183

Modified: 2025-06-12T16:06:20.180

Link: CVE-2025-5986

cve-icon Redhat

Severity : Important

Publid Date: 2025-06-10T00:00:00Z

Links: CVE-2025-5986 - Bugzilla