CVE-2026-26230 PUBLISHED

Team Admin Privilege Escalation to Demote Members to Guest

Assigner: Mattermost
Reserved: 13.02.2026 Published: 16.03.2026 Updated: 17.03.2026

Mattermost versions 10.11.x <= 10.11.10 fail to properly validate permission requirements in the team member roles API endpoint which allows team administrators to demote members to guest role. Mattermost Advisory ID: MMSA-2025-00531

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
CVSS Score: 3.8

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	Low
Privileges Required	High	Integrity Impact	Low
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 10.11.0 to 10.11.10 (incl.) Version 11.4.0 is unaffected Version 10.11.11 is unaffected

Solutions

Update Mattermost to versions 11.4.0, 10.11.11 or higher.

Credits

hackit_bharat finder

References

MMSA-2025-00531

Problem Types

CWE-863: Incorrect Authorization CWE