Home/CVE/A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to the user's de
CVE

CVE-2025-5986

A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to the user's de

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 was fixed in Thunderbird 128.11.1 and Thunderbird 139.0.2.

MEDIUM · CVSS 6.5 EPSS 0.00583
Monitor
  • No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-451User Interface (UI) Misrepresentation of Critical Information
▤

Affected Products & Versions

2
mozilla thunderbird< 128.11.1
mozilla thunderbird>= 135.0 and < 139.0.2
▣

Scoring & Timeline

6.5
MEDIUM · CVSS v3.1 · security@mozilla.org
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD11 Jun 2025 · 12:15 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

16
usnUSN-7663-1
suse-csafopenSUSE-SU-2025:15204-1
suse-csafSUSE-SU-2025:02158-1
rhsaRHSA-2025:10246Moderate
rhsaRHSA-2025:10159Moderate
🔗

References & Sources

4
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1958580%2C1968012Broken Link
https://www.mozilla.org/security/advisories/mfsa2025-49/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-50/Vendor Advisory
https://lists.debian.org/debian-lts-announce/2025/07/msg00002.html
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