Improper file ownership validation in the Boards API allows unauthorised file access
Priority LOW 30CWE-639Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-639.
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs.. Mattermost Advisory ID: MMSA-2026-00620
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00149 4th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.7.0, 11.6.1, 11.5.4 +2github.com/mattermost/mattermost-server (Go): 11.6.1, 11.5.4, 11.4.5 +1
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
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Mattermost | Mattermost | 11.6.0 – 11.6.0; 11.5.0 – 11.5.3; 11.4.0 – 11.4.4; 10.11.0 – 10.11.14 | 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 | Patch available | CNA |
| — | github.com/mattermost/mattermost-server (Go) | 11.6.0 to before 11.6.1 | 11.6.1 | Patch available | GHSA-7pf2-9c95-w332 |
| — | github.com/mattermost/mattermost-server (Go) | 11.5.0 to before 11.5.4 | 11.5.4 | Patch available | GHSA-7pf2-9c95-w332 |
| — | github.com/mattermost/mattermost-server (Go) | 11.4.0 to before 11.4.5 | 11.4.5 | Patch available | GHSA-7pf2-9c95-w332 |
| — | github.com/mattermost/mattermost-server (Go) | 10.11.0 to before 10.11.15 | 10.11.15 | Patch available | GHSA-7pf2-9c95-w332 |
- Mattermost VendorMattermost Affected 11.6.0 – 11.6.0; 11.5.0 – 11.5.3; 11.4.0 – 11.4.4; 10.11.0 – 10.11.14 Fixed in 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 Patch available CNA
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 11.6.0 to before 11.6.1 Fixed in 11.6.1 Patch available GHSA-7pf2-9c95-w332
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 11.5.0 to before 11.5.4 Fixed in 11.5.4 Patch available GHSA-7pf2-9c95-w332
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 11.4.0 to before 11.4.5 Fixed in 11.4.5 Patch available GHSA-7pf2-9c95-w332
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 10.11.0 to before 10.11.15 Fixed in 10.11.15 Patch available GHSA-7pf2-9c95-w332
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | 10.11.0 to before 10.11.15; 11.4.0 to before 11.4.5; 11.5.0 to before 11.5.4; 11.6.0 to before 11.6.1 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.15; 11.4.0 to before 11.4.5; 11.5.0 to before 11.5.4; 11.6.0 to before 11.6.1 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15
- Fix · GHSA-7pf2-9c95-w332 github.com/mattermost/mattermost-server (Go) Fixed in 11.6.1 Advisory →
- Fix · GHSA-7pf2-9c95-w332 github.com/mattermost/mattermost-server (Go) Fixed in 11.5.4 Advisory →
- Fix · GHSA-7pf2-9c95-w332 github.com/mattermost/mattermost-server (Go) Fixed in 11.4.5 Advisory →
- Fix · GHSA-7pf2-9c95-w332 github.com/mattermost/mattermost-server (Go) Fixed in 10.11.15 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-3473
- 2026-10-03 Alias added: GHSA-7pf2-9c95-w332
References
More Mattermost Server vulnerabilities
- TI-2025-18933 Arbitrary file read in Mattermost Boards via import & export board archive CVSS 3.1CRITICAL 9.9
- TI-2025-04465 Path Traversal Leading to RCE by Any Authenticated Mattermost User CVSS 3.1CRITICAL 9.9
- TI-2017-14068 An issue was discovered in Mattermost Server before 3.6.2. CVSS 3.1CRITICAL 9.8
- TI-2017-14060 An issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. CVSS 3.1CRITICAL 9.8
- TI-2017-14048 An issue was discovered in Mattermost Server before 4.1.0, 4.0.4, and 3.10.3. CVSS 3.1CRITICAL 9.8
- TI-2025-14360 Arbitrary file read via block duplication in Mattermost Boards CVSS 3.1CRITICAL 9.9
Sources
- CVE-2026-3473 · CVE Program
- CVE-2026-3473 · NVD
- FIRST EPSS
- GHSA-7pf2-9c95-w332 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences