Command Hijacking Vulnerability in Mattermost by Mattermost
CVE-2026-28732

4.3MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
18 May 2026

What is CVE-2026-28732?

Mattermost versions 11.5.x up to 11.5.1, 10.11.x up to 10.11.13, and 11.4.x up to 11.4.3 are subject to a vulnerability that compromises the uniqueness of slash command trigger words during updates. This issue allows an authenticated user with the 'Manage Own Slash Commands' permission to alter their own command trigger to match an already registered system or custom command. As a result, this could lead to unauthorized command hijacking and impersonation, permitting malicious actions by exploiting the command update API.

Affected Version(s)

Mattermost 11.5.0 <= 11.5.1

Mattermost 10.11.0 <= 10.11.13

Mattermost 11.4.0 <= 11.4.3

References

https://mattermost.com/security-updates
vendor-advisory

CVSS V3.1

Score:
4.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

mr_anksec
.