Description
Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate team membership when processing channel mentions which allows authenticated users to determine the existence of teams and their URL names via posting channel shortlinks and observing the channel_mentions property in the API response. Mattermost Advisory ID: MMSA-2025-00563
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 11.1.0 – ≤ 11.1.2, 10.11.0 – ≤ 10.11.9, 11.2.0 – ≤ 11.2.1 | 11.3.0 |
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 |
| openSUSE Leap 15.6 | govulncheck-vulndb | 0.0.20260226T182644-150000.1.149.1 | SUSE-SU-2026:0757-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | >= 11.1.0 | — | GHSA-57cc-2pf4-mhmx |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0 | — | GHSA-57cc-2pf4-mhmx |
| Go | github.com/mattermost/mattermost-server | >= 11.2.0 | — | GHSA-57cc-2pf4-mhmx |
| Go | github.com/mattermost/mattermost-server | < 5.3.2-0.20251209134645-761e56bb11cc | 5.3.2-0.20251209134645-761e56bb11cc | GHSA-57cc-2pf4-mhmx |
| Go | github.com/mattermost/mattermost-server | all versions | — | GO-2026-4521 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0+incompatible | — | GO-2026-4521 |
| Go | github.com/mattermost/mattermost-server | >= 11.1.0+incompatible | — | GO-2026-4521 |
| Go | github.com/mattermost/mattermost-server | >= 11.2.0+incompatible | — | GO-2026-4521 |
| Go | github.com/mattermost/mattermost-server/v5 | all versions | — | GO-2026-4521 |
| Go | github.com/mattermost/mattermost-server/v6 | all versions | — | GO-2026-4521 |
| Go | github.com/mattermost/mattermost/server/v8 | < 8.0.0-20251209134645-761e56bb11cc | 8.0.0-20251209134645-761e56bb11cc | GHSA-57cc-2pf4-mhmx |
Advisories 2
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
- SUSE-SU-2026:0757-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Mar 4, 2026
References
- MMSA-2025-00563 vendor-advisory