CVE-2026-7387

Analyzed Analyzed - Analysis Complete

Privilege Escalation in Mattermost via Group Sync API

Publication date: 2026-06-12

Last updated on: 2026-06-18

Assigner: Mattermost, Inc.

Description

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 Mattermost fails 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

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-06-12

Last Modified

2026-06-18

Generated

2026-07-03

AI Q&A

2026-06-12

EPSS Evaluated

2026-07-01

NVD

CVE-2026-7387

EUVD

EUVD-2026-36503

Affected Vendors & Products

Vendor	Product	Version / Range
mattermost	mattermost_server	From 10.11.0 (inc) to 10.11.17 (exc)
mattermost	mattermost_server	From 11.5.0 (inc) to 11.5.5 (exc)
mattermost	mattermost_server	From 11.6.0 (inc) to 11.6.2 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-863	The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

Attack-Flow Graph

Executive Summary

This vulnerability exists in Mattermost versions 11.6.x up to 11.6.1, 11.5.x up to 11.5.4, and 10.11.x up to 10.11.16. It occurs because Mattermost does not require proper role-management authorization when setting the scheme_admin flag on group syncable link and patch endpoints.

As a result, a user who has group-link permissions can exploit this flaw by crafting specific API requests to escalate their own privileges and those of group members to team or channel admin.

Impact Analysis

This vulnerability can have a significant impact because it allows unauthorized privilege escalation.

An attacker with group-link permissions can elevate themselves and other group members to team or channel administrators.
This can lead to unauthorized access to sensitive information, modification of team or channel settings, and potential disruption of normal operations.
Given the CVSS base score of 8.8, the vulnerability is considered high severity, affecting confidentiality, integrity, and availability.

Compliance Impact

This vulnerability allows unauthorized privilege escalation to team or channel admin roles via crafted API requests, which can lead to unauthorized access and modification of sensitive data.

Such unauthorized access and privilege escalation could potentially violate compliance requirements under standards like GDPR and HIPAA, which mandate strict access controls and protection of sensitive information.

However, specific impacts on compliance are not detailed in the provided information.

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