CVE-2025-53971

Channel and Team Membership APIs inadvertently allow loss of Member privileges.

3.8 LowFix available

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: High
User interaction: None

What an attacker can affect

Confidentiality: Low
Integrity: Low
Availability: None

Exploit likelihood

0.20%Up 0.2 points since Aug 21, 2025

What each source reports

CVE List Score used 3.8

Channel and Team Membership APIs inadvertently allow loss of Member privileges.

Record: CVE-2025-53971
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-863
Updated: 2026-11-02

EUVDEUVD-2025-25413 3.8

Record: EUVD-2025-25413
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-4276-cm8c-788h 3.8

Mattermost Fails to Properly Validate Team Role Modification

Record: GHSA-4276-cm8c-788h
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-863
Updated: 2026-11-02

NVD 3.8

Record: CVE-2025-53971
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-863
Updated: 2026-11-02

OSV 3.8

Channel and Team Membership APIs inadvertently allow loss of Member privileges.

Record: CVE-2025-53971
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-863
Updated: 2026-11-02

OSVGHSA-4276-cm8c-788h 3.8

Mattermost Fails to Properly Validate Team Role Modification

Record: GHSA-4276-cm8c-788h
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-863
Updated: 2026-11-02

OSVGO-2025-3902 No score

Mattermost Fails to Properly Validate Team Role Modification in github.com/mattermost/mattermost-server

Mattermost Fails to Properly Validate Team Role Modification in github.com/mattermost/mattermost-server

Record: GO-2025-3902
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`github.com/mattermost/mattermost-server` Go	10.5.0 to 10.5.8	10.5.9
`github.com/mattermost/mattermost-server` Go	9.11.0 to 9.11.17	9.11.18
`github.com/mattermost/mattermost/server/v8` Go	before 8.0.0-20250721095846-c602a4a78e1f	8.0.0-20250721095846-c602a4a78e1f
`github.com/mattermost/mattermost-server/v5` Go	through 5.39.3	None known
`github.com/mattermost/mattermost-server/v6` Go	through 6.7.2	None known
`github.com/mattermost/mattermost-server` Go	10.5.0 up to 10.5.9	10.5.9
`github.com/mattermost/mattermost-server` Go	9.11.0 up to 9.11.18	9.11.18
`github.com/mattermost/mattermost-server` Go	9.11.0+incompatible up to 9.11.18+incompatible, 10.5.0+incompatible up to 10.5.9+incompatible	9.11.18+incompatible10.5.9+incompatible
`github.com/mattermost/mattermost-server/v5` Go	All versions	None known
`github.com/mattermost/mattermost-server/v6` Go	All versions	None known

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-53971 is a low vulnerability (CVSS 3.8) in Mattermost, published August 21, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.20%, the 10th percentile. Fixed in github.com/mattermost/mattermost-server 10.5.9.