CVE-2026-7387 — Vulnerability in...

HIGH

Mattermost doesn't require role-management authorization when setting the scheme_admin flag on group syncable link and patch endpoints

Published June 12, 2026Updated August 26, 2026Source: osv

Summary

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to require role-management authorization when setting the scheme_admin flag on group syncable link and patch endpoints, which allows a user with group-link permissions to escalate themselves and group members to team or channel admin via crafted API requests. Mattermost Advisory ID: MMSA-2026-00665

Advisory Timeline

First published June 12, 2026 (122 days ago).
Last revised August 26, 2026 — 74 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

Update github.com/mattermost/mattermost-server to 11.5.5 or later

go get github.com/mattermost/mattermost-server@v11.5.5

Update github.com/mattermost/mattermost-server to 10.11.17 or later

go get github.com/mattermost/mattermost-server@v10.11.17

Update github.com/mattermost/mattermost-server to 11.6.1 or later

go get github.com/mattermost/mattermost-server@v11.6.1

Update github.com/mattermost/mattermost/server/v8 to 8.0.0-20260506065351-202d125afa87 or later

go get github.com/mattermost/mattermost/server/v8@v8.0.0-20260506065351-202d125afa87

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (4)

Affects 1 ecosystem: go (2).

Package	Ecosystem	Affected	Fixed In
github.com/mattermost/mattermost-server	go	All versions	11.5.5
github.com/mattermost/mattermost-server	go	All versions	10.11.17
github.com/mattermost/mattermost-server	go	11.6.0	11.6.1
github.com/mattermost/mattermost/server/v8	go	All versions	8.0.0-20260506065351-202d125afa87

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CWE-863
Incorrect AuthorizationMITRE

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 8.8 score means for each attack dimension.

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

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

References

Frequently Asked Questions

What is CVE-2026-7387?: Mattermost doesn't require role-management authorization when setting the scheme_admin flag on group syncable link and patch endpoints This vulnerability has been assigned a severity rating of HIGH (CVSS score: 8.8/10).
How do I check if my project is affected by CVE-2026-7387?: CVE-2026-7387 affects github.com/mattermost/mattermost-server and github.com/mattermost/mattermost/server/v8. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-7387 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score

8.8

High exploitability or significant impact. Prioritize remediation within days.

Also Known As

GHSA-6hxm-w4hv-vgvw

GO-2026-6280

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