CVE-2026-28732 PUBLISHED

Slash command trigger-word update allowed command hijacking

Assigner: Mattermost
Reserved: 16.03.2026 Published: 18.05.2026 Updated: 18.05.2026

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 Fail to enforce slash command trigger-word uniqueness during command updates which allows an authenticated team member with Manage Own Slash Commands permission to hijack and impersonate existing system or custom slash commands via editing their own slash command trigger to an already-registered trigger through the command update API. Mattermost Advisory ID: MMSA-2026-00597

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
CVSS Score: 4.3

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

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.5.0 to 11.5.1 (incl.) affected from 10.11.0 to 10.11.13 (incl.) affected from 11.4.0 to 11.4.3 (incl.) Version 11.6.0 is unaffected Version 11.5.2 is unaffected Version 10.11.14 is unaffected Version 11.4.4 is unaffected

Solutions

Update Mattermost to versions 11.6.0, 11.5.2, 10.11.14, 11.4.4 or higher.

Credits

mr_anksec finder

References

MMSA-2026-00597

Problem Types

CWE-863: Incorrect Authorization CWE