Unsolicited File Download, Disk Space Exhaustion, and Credential Leakage via mailbox:/// Links
Priority LOW 30CWE-451Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Spoofing
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 13 fixed, 3 without a fix
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat. Impact type from CWE-451.
Summary
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.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00605 49th percentileScored 2026-11-07
Fix Partial Thunderbird (Mozilla): 128.11.1, 139.0.2Red Hat: 10 advisoriesRed Hat: 13 fixed, 3 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
- Fix · CNA Thunderbird (Mozilla) Fixed in 128.11.1, 139.0.2
Red Hat 10 advisories
- RHSA-2025:10246 Released 2025-07-02 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream (v. 8) thunderbird-128.12.0-1.el8_10
- RHSA-2025:10196 Released 2025-07-02 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream (v. 9) thunderbird-128.12.0-1.el9_6
- RHSA-2025:10195 Released 2025-07-02 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream (v. 10) thunderbird-128.12.0-1.el10_0
Show 7 more Red Hat advisories
- RHSA-2025:10164 Released 2025-07-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream AUS (v.8.6) thunderbird-128.12.0-1.el8_6
- Red Hat Enterprise Linux AppStream E4S (v.8.6) thunderbird-128.12.0-1.el8_6
- Red Hat Enterprise Linux AppStream TUS (v.8.6) thunderbird-128.12.0-1.el8_6
- RHSA-2025:10159 Released 2025-07-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream EUS (v.9.4) thunderbird-128.12.0-1.el9_4
- RHSA-2025:10160 Released 2025-07-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream E4S (v.9.2) thunderbird-128.12.0-1.el9_2
- RHSA-2025:10163 Released 2025-07-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream E4S (v.8.8) thunderbird-128.12.0-1.el8_8
- Red Hat Enterprise Linux AppStream TUS (v.8.8) thunderbird-128.12.0-1.el8_8
- RHSA-2025:10165 Released 2025-07-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream AUS (v.8.4) thunderbird-128.12.0-1.el8_4
- RHSA-2025:10161 Released 2025-07-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream E4S (v.9.0) thunderbird-128.12.0-1.el9_0
- RHSA-2025:10166 Released 2025-07-01 · Red Hat rating Importantthunderbird security update
- Red Hat Enterprise Linux AppStream AUS (v. 8.2) thunderbird-128.12.0-1.el8_2
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux AppStream (v. 10) | Fixed | RHSA-2025:10195 |
| Red Hat Enterprise Linux AppStream (v. 8) | Fixed | RHSA-2025:10246 |
| Red Hat Enterprise Linux AppStream (v. 9) | Fixed | RHSA-2025:10196 |
| Red Hat Enterprise Linux AppStream AUS (v. 8.2) | Fixed | RHSA-2025:10166 |
| Red Hat Enterprise Linux AppStream AUS (v.8.4) | Fixed | RHSA-2025:10165 |
| Red Hat Enterprise Linux AppStream AUS (v.8.6) | Fixed | RHSA-2025:10164 |
| Red Hat Enterprise Linux AppStream E4S (v.8.6) | Fixed | RHSA-2025:10164 |
| Red Hat Enterprise Linux AppStream E4S (v.8.8) | Fixed | RHSA-2025:10163 |
| Red Hat Enterprise Linux AppStream E4S (v.9.0) | Fixed | RHSA-2025:10161 |
| Red Hat Enterprise Linux AppStream E4S (v.9.2) | Fixed | RHSA-2025:10160 |
| Red Hat Enterprise Linux AppStream EUS (v.9.4) | Fixed | RHSA-2025:10159 |
| Red Hat Enterprise Linux AppStream TUS (v.8.6) | Fixed | RHSA-2025:10164 |
| Red Hat Enterprise Linux AppStream TUS (v.8.8) | Fixed | RHSA-2025:10163 |
Timeline
- 2026-10-02 Threatist record created from CVE-2025-5986
- 2026-10-03 Alias added: GHSA-q7fj-77gc-45xq
References
More Mozilla Thunderbird vulnerabilities
- TI-2024-08981 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.8
- TI-2022-09832 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.6
- TI-2019-08769 Improper input validation in Mozilla Firefox ESR KEVCVSS 3.1CRITICAL 10.0
- TI-2010-03577 Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before… KEVCVSS 3.1CRITICAL 9.8
- TI-2023-04799 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
- TI-2023-04477 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
Sources
- CVE-2025-5986 · CVE Program
- CVE-2025-5986 · NVD
- FIRST EPSS
- GHSA-q7fj-77gc-45xq · GitHub Advisory Database · CC BY 4.0
- CVE-2025-5986 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences