Description
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to check the create_post channel permission during post edit operations which allows an authenticated attacker with revoked posting privileges to modify their existing posts via direct API requests to the post update and patch endpoints.. Mattermost Advisory ID: MMSA-2026-00627
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 11.5.0 – ≤ 11.5.1, 10.11.0 – ≤ 10.11.13, 11.4.0 – ≤ 11.4.3 | 11.6.0 |
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 | < 5.3.2-0.20260316171743-090408f09f53 | 5.3.2-0.20260316171743-090408f09f53 | GHSA-v549-xx3c-6pc8 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0+incompatible, < 10.11.14+incompatible · >= 11.4.0+incompatible, < 11.4.4+incompatible · >= 11.5.0+incompatible, < 11.5.2+incompatible | 10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatible | GO-2026-5651 |
| Go | github.com/mattermost/mattermost-server/v5 | all versions | — | GO-2026-5651 |
| Go | github.com/mattermost/mattermost-server/v6 | all versions | — | GO-2026-5651 |
| Go | github.com/mattermost/mattermost/server/v8 | >= 10.11.0, < 10.11.14 | 10.11.14 | GHSA-v549-xx3c-6pc8 |
| Go | github.com/mattermost/mattermost/server/v8 | >= 11.4.0, < 11.4.4 | 11.4.4 | GHSA-v549-xx3c-6pc8 |
| Go | github.com/mattermost/mattermost/server/v8 | < 8.0.0-20260316171743-090408f09f53 | 8.0.0-20260316171743-090408f09f53 | GHSA-v549-xx3c-6pc8 |
| Go | github.com/mattermost/mattermost/server/v8 | >= 11.5.0, < 11.5.2 | 11.5.2 | GHSA-v549-xx3c-6pc8 |
Advisories 1
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
References
- MMSA-2026-00627 vendor-advisory