Description
Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, 10.11.x <= 10.11.7 fails to validate user channel membership when attaching Mattermost posts as comments to Jira issues, which allows an authenticated attacker with access to the Jira plugin to read post content and attachments from channels they do not have access to.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 11.1.0 – ≤ 11.1.0, 11.0.0 – ≤ 11.0.5, 10.12.0 – ≤ 10.12.3, 10.11.0 – ≤ 10.11.7 | 11.2.0 |
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 | >= 10.11.0, < 10.11.8 | 10.11.8 | GHSA-fmqf-pmcm-8cx9 |
| Go | github.com/mattermost/mattermost-server | >= 10.12.0, < 10.12.4 | 10.12.4 | GHSA-fmqf-pmcm-8cx9 |
| Go | github.com/mattermost/mattermost-server | >= 11.0.0, < 11.0.6 | 11.0.6 | GHSA-fmqf-pmcm-8cx9 |
| Go | github.com/mattermost/mattermost-server | >= 11.1.0, < 11.1.1 | 11.1.1 | GHSA-fmqf-pmcm-8cx9 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0+incompatible, < 10.11.8+incompatible · >= 10.12.0+incompatible, < 10.12.4+incompatible · >= 11.0.1+incompatible, < 11.0.6+incompatible · >= 11.1.0+incompatible, < 11.1.1+incompatible | 10.11.8+incompatible, 10.12.4+incompatible, 11.0.6+incompatible, 11.1.1+incompatible | GO-2025-4259 |
| Go | github.com/mattermost/mattermost-server/v5 | all versions | — | GO-2025-4259 |
| Go | github.com/mattermost/mattermost-server/v6 | all versions | — | GO-2025-4259 |
| Go | github.com/mattermost/mattermost/server/v8 | < 8.0.0-20251121122154-b57c297c6d7 | 8.0.0-20251121122154-b57c297c6d7 | GHSA-fmqf-pmcm-8cx9 |
| Go | github.com/mattermost/mattermost/server/v8 | all versions | — | GO-2025-4259 |
Advisories 3
- 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
- WID-SEC-2025-2712 Mattermost: Schwachstelle ermöglicht Offenlegung von Informationen BSI CERT-Bund (WID) · Feb 26, 2026