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
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 11.2.0 – ≤ 11.2.2, 10.11.0 – ≤ 10.11.10, 11.4.0 – ≤ 11.4.0, 11.3.0 – ≤ 11.3.1 | 11.5.0 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | govulncheck-vulndb | 0.0.20260723T184607-160000.1.1 | openSUSE-SU-2026:21483-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | >= 10.11.0-rc1+incompatible, < 10.11.11+incompatible · >= 11.2.0-rc1+incompatible, < 11.2.3+incompatible · >= 11.3.0-rc1+incompatible, < 11.3.2+incompatible · >= 11.4.0+incompatible, < 11.4.1+incompatible | 10.11.11+incompatible, 11.2.3+incompatible, 11.3.2+incompatible, 11.4.1+incompatible | GO-2026-5512 |
| Go | github.com/mattermost/mattermost-server/v5 | all versions | — | GO-2026-5512 |
| Go | github.com/mattermost/mattermost-server/v6 | all versions | — | GO-2026-5512 |
| Go | github.com/mattermost/mattermost/server/v8 | >= 11.4.0, < 11.4.1 | 11.4.1 | GHSA-mpc7-mm28-f6wq |
| Go | github.com/mattermost/mattermost/server/v8 | >= 11.3.0-rc1, < 11.3.2 | 11.3.2 | GHSA-mpc7-mm28-f6wq |
| Go | github.com/mattermost/mattermost/server/v8 | >= 11.2.0-rc1, < 11.2.3 | 11.2.3 | GHSA-mpc7-mm28-f6wq |
| Go | github.com/mattermost/mattermost/server/v8 | >= 10.11.0-rc1, < 10.11.11 | 10.11.11 | GHSA-mpc7-mm28-f6wq |
| Go | github.com/mattermost/mattermost/server/v8 | >= 8.0.0-20260105080200-d27a2195068d, < 8.0.0-20260217110922-b7d4a1f1f59b | 8.0.0-20260217110922-b7d4a1f1f59b | GHSA-mpc7-mm28-f6wq |
Advisories 1
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
References
- MMSA-2026-00594 vendor-advisory