CVE-2026-28732
Medium
Description
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
SeverityMedium
CVSS4.3
Exploit probability—
Product
Mattermost Server
PublishedMay 18, 2026
First seenMay 18, 2026
Weakness typeCWE-863Incorrect authorization
How to fix
Update
- mattermost mattermost_server10.11.14, 11.4.4, 11.5.2 or later
- github.com/mattermost/mattermost/server/v811.5.2, 10.11.14, 11.4.4, 8.0.0-20260306123948-f5fe8ded6b63 or later
- github.com/mattermost/mattermost-server5.3.2-0.20260306123948-f5fe8ded6b63, 10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatible or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 10.11.0 ≤ v < 10.11.14, 11.4.0 ≤ v < 11.4.4, 11.5.0 ≤ v < 11.5.2 | 10.11.14, 11.4.4, 11.5.2 |
| github.com/mattermost/mattermost/server/v8Go | 11.5.0 ≤ v < 11.5.2, 10.11.0 ≤ v < 10.11.14, 11.4.0 ≤ v < 11.4.4, v < 8.0.0-20260306123948-f5fe8ded6b63 | 11.5.2, 10.11.14, 11.4.4, 8.0.0-20260306123948-f5fe8ded6b63 |
| github.com/mattermost/mattermost-serverGo | v < 5.3.2-0.20260306123948-f5fe8ded6b63, 10.11.0+incompatible ≤ v < 10.11.14+incompatible, 11.4.0+incompatible ≤ v < 11.4.4+incompatible, 11.5.0+incompatible ≤ v < 11.5.2+incompatible | 5.3.2-0.20260306123948-f5fe8ded6b63, 10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatible |
| github.com/mattermost/mattermost-server/v5Go | No range specified | — |
| github.com/mattermost/mattermost-server/v6Go | No range specified | — |
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