---
title: "CVE-2025-5986\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2025-5986?format=md
keywords: index, follow
---

# CVE-2025-5986

Publication date 11 June 2025

Last updated 26 June 2026

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**6.5 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2025-5986?format=md#impact-score)

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## 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
was fixed in Thunderbird 128.11.1 and Thunderbird 139.0.2.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| thunderbird | 25.04 plucky | Not affected |
| 24.10 oracular | Ignored end of life, was needs-triage |
| 24.04 LTS noble | Not affected |
| 22.04 LTS jammy | Fixed 1:128.12.0+build1-0ubuntu0.22.04.1 |
| 20.04 LTS focal | Not in release |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

6.5 · Medium

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Privileges required | None |
  | User interaction | Required |
  | Scope | Unchanged |
  | Confidentiality impact | None |
  | Integrity impact | None |
  | Availability impact | High |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 6.5 · Medium |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-5986)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2025-5986)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2025-5986)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2025-5986)

### Related Ubuntu Security Notices (USN)

+ [USN-7663-1](https://usn.ubuntu.com/USN-7663-1)
+ Thunderbird vulnerabilities
+ 22 July 2025

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2025-5986>
* <https://www.mozilla.org/en-US/security/advisories/mfsa2025-49/#CVE-2025-5986>
* <https://bugzilla.mozilla.org/buglist.cgi?bug_id=1958580%2C1968012>
* <https://www.mozilla.org/security/advisories/mfsa2025-49/>
* <https://www.mozilla.org/security/advisories/mfsa2025-50/>