Channel and Team Membership APIs inadvertently allow loss of Member privileges.
Priority LOW 17CWE-863Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- High
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-863.
Summary
Mattermost versions 10.5.x <= 10.5.8, 9.11.x <= 9.11.17 fail to properly validate authorization for team scheme role modifications which allows Team Admins to demote Team Members to Guests via the PUT /api/v4/teams/team-id/members/user-id/schemeRoles API endpoint.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00203 10th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 10.10.0, 10.5.9, 9.11.18github.com/mattermost/mattermost-server (Go): 10.5.9, 9.11.18+1 more product
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 | 10.5.0 – 10.5.8; 9.11.0 – 9.11.17 | 10.10.0, 10.5.9, 9.11.18 | Patch available | CNA |
| — | github.com/mattermost/mattermost-server (Go) | 10.5.0 to before 10.5.9 | 10.5.9 | Patch available | GHSA-4276-cm8c-788h |
| — | github.com/mattermost/mattermost-server (Go) | 9.11.0 to before 9.11.18 | 9.11.18 | Patch available | GHSA-4276-cm8c-788h |
| — | github.com/mattermost/mattermost/server/v8 (Go) | before 8.0.0-20250721095846-c602a4a78e1f | 8.0.0-20250721095846-c602a4a78e1f | Patch available | GHSA-4276-cm8c-788h |
| — | github.com/mattermost/mattermost-server/v5 (Go) | up to 5.39.3 | — | No fix listed | GHSA-4276-cm8c-788h |
| — | github.com/mattermost/mattermost-server/v6 (Go) | up to 6.7.2 | — | No fix listed | GHSA-4276-cm8c-788h |
- Mattermost VendorMattermost Affected 10.5.0 – 10.5.8; 9.11.0 – 9.11.17 Fixed in 10.10.0, 10.5.9, 9.11.18 Patch available CNA
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 10.5.0 to before 10.5.9 Fixed in 10.5.9 Patch available GHSA-4276-cm8c-788h
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 9.11.0 to before 9.11.18 Fixed in 9.11.18 Patch available GHSA-4276-cm8c-788h
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected before 8.0.0-20250721095846-c602a4a78e1f Fixed in 8.0.0-20250721095846-c602a4a78e1f Patch available GHSA-4276-cm8c-788h
- github.com/mattermost/mattermost-server/v5 (Go) Vendor— Affected up to 5.39.3 Fixed in — No fix listed GHSA-4276-cm8c-788h
- github.com/mattermost/mattermost-server/v6 (Go) Vendor— Affected up to 6.7.2 Fixed in — No fix listed GHSA-4276-cm8c-788h
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | 9.11.0 to before 9.11.18; 10.5.0 to before 10.5.9 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 9.11.0 to before 9.11.18; 10.5.0 to before 10.5.9 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 10.10.0, 10.5.9, 9.11.18
- Fix · GHSA-4276-cm8c-788h github.com/mattermost/mattermost-server (Go) Fixed in 10.5.9 Advisory →
- Fix · GHSA-4276-cm8c-788h github.com/mattermost/mattermost-server (Go) Fixed in 9.11.18 Advisory →
- Fix · GHSA-4276-cm8c-788h github.com/mattermost/mattermost/server/v8 (Go) Fixed in 8.0.0-20250721095846-c602a4a78e1f Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2025-53971
- 2026-10-03 Alias added: GHSA-4276-cm8c-788h
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-2025-53971 · CVE Program
- CVE-2025-53971 · NVD
- FIRST EPSS
- GHSA-4276-cm8c-788h · GitHub Advisory Database · CC BY 4.0
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