Description
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs.. Mattermost Advisory ID: MMSA-2026-00620
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 11.6.0 – ≤ 11.6.0, 11.5.0 – ≤ 11.5.3, 11.4.0 – ≤ 11.4.4, 10.11.0 – ≤ 10.11.14 | 11.7.0 |
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 | >= 11.6.0, < 11.6.1 | 11.6.1 | GHSA-7pf2-9c95-w332 |
| Go | github.com/mattermost/mattermost-server | >= 11.5.0, < 11.5.4 | 11.5.4 | GHSA-7pf2-9c95-w332 |
| Go | github.com/mattermost/mattermost-server | >= 11.4.0, < 11.4.5 | 11.4.5 | GHSA-7pf2-9c95-w332 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0, < 10.11.15 | 10.11.15 | GHSA-7pf2-9c95-w332 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0+incompatible, < 10.11.15+incompatible · >= 11.4.0+incompatible, < 11.4.5+incompatible · >= 11.5.0+incompatible, < 11.5.4+incompatible · >= 11.6.0+incompatible, < 11.6.1+incompatible | 10.11.15+incompatible, 11.4.5+incompatible, 11.5.4+incompatible, 11.6.1+incompatible | GO-2026-5817 |
Advisories 2
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
- WID-SEC-2026-1243 Mattermost: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff BSI CERT-Bund (WID) · May 25, 2026
References
- MMSA-2026-00620 vendor-advisory