CVE-2026-3115
Medium
Description
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
SeverityMedium
CVSS4.3
Exploit probability—
Product
Mattermost Server
PublishedMar 26, 2026
First seenMar 26, 2026
Weakness typeCWE-863Incorrect authorization
How to fix
Update
- mattermost mattermost_server10.11.11, 11.2.3, 11.3.2 or later
- github.com/mattermost/mattermost/server/v811.4.1, 11.3.2, 11.2.3, 10.11.11, 8.0.0-20260217110922-b7d4a1f1f59b or later
- github.com/mattermost/mattermost-server10.11.11+incompatible, 11.2.3+incompatible, 11.3.2+incompatible, 11.4.1+incompatible or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 10.11.0 ≤ v < 10.11.11, 11.2.0 ≤ v < 11.2.3, 11.3.0 ≤ v < 11.3.2, 11.4.0 | 10.11.11, 11.2.3, 11.3.2 |
| github.com/mattermost/mattermost/server/v8Go | 11.4.0 ≤ v < 11.4.1, 11.3.0-rc1 ≤ v < 11.3.2, 11.2.0-rc1 ≤ v < 11.2.3, 10.11.0-rc1 ≤ v < 10.11.11, 8.0.0-20260105080200-d27a2195068d ≤ v < 8.0.0-20260217110922-b7d4a1f1f59b | 11.4.1, 11.3.2, 11.2.3, 10.11.11, 8.0.0-20260217110922-b7d4a1f1f59b |
| github.com/mattermost/mattermost-serverGo | 10.11.0-rc1+incompatible ≤ v < 10.11.11+incompatible, 11.2.0-rc1+incompatible ≤ v < 11.2.3+incompatible, 11.3.0-rc1+incompatible ≤ v < 11.3.2+incompatible, 11.4.0+incompatible ≤ v < 11.4.1+incompatible | 10.11.11+incompatible, 11.2.3+incompatible, 11.3.2+incompatible, 11.4.1+incompatible |
| github.com/mattermost/mattermost-server/v5Go | No range specified | — |
| github.com/mattermost/mattermost-server/v6Go | No range specified | — |
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