GHSA-mpc7-mm28-f6wq
Mattermost allows authenticated guest users to enumerate user IDs outside their allowed visibility scope
Packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| Go | github.com/mattermost/mattermost/server/v8 | >= 11.4.0, < 11.4.1 | 11.4.1 |
| Go | github.com/mattermost/mattermost/server/v8 | >= 11.3.0-rc1, < 11.3.2 | 11.3.2 |
| Go | github.com/mattermost/mattermost/server/v8 | >= 11.2.0-rc1, < 11.2.3 | 11.2.3 |
| Go | github.com/mattermost/mattermost/server/v8 | >= 10.11.0-rc1, < 10.11.11 | 10.11.11 |
| Go | github.com/mattermost/mattermost/server/v8 | >= 8.0.0-20260105080200-d27a2195068d, < 8.0.0-20260217110922-b7d4a1f1f59b | 8.0.0-20260217110922-b7d4a1f1f59b |
Details
As written in the advisory (Markdown source, shown as plain text).
Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to apply view restrictions when retrieving group member IDs, which allows authenticated guest users to enumerate user IDs outside their allowed visibility scope via the group retrieval endpoint. Mattermost Advisory ID: MMSA-2026-00594.
References
External links from the advisory. They lead to third-party sites.