Vulnerability · Published May 18, 2026 · Assigned by Mattermost
CVE-2026-3637Mattermost fails to enforce create_post permission when editing posts
Medium 4.3
In plain English
A medium-severity missing authorization in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 4% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | 10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatible | GO-2026-5651 |
| Go | github.com/mattermost/mattermost-server | 5.3.2-0.20260316171743-090408f09f53 | GHSA-v549-xx3c-6pc8 |
| Go | github.com/mattermost/mattermost-server/v5 | no fix listed | GO-2026-5651 |
| Go | github.com/mattermost/mattermost-server/v6 | no fix listed | GO-2026-5651 |
| Go | github.com/mattermost/mattermost/server/v8 | 10.11.14 | GHSA-v549-xx3c-6pc8 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20260316171743-090408f09f53 | GO-2026-5651 |
| Go | github.com/mattermost/mattermost/server/v8 | 11.4.4 | GHSA-v549-xx3c-6pc8 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20260316171743-090408f09f53 | GHSA-v549-xx3c-6pc8 |
| Go | github.com/mattermost/mattermost/server/v8 | 11.5.2 | GHSA-v549-xx3c-6pc8 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 11.5.0 – through 11.5.110.11.0 – through 10.11.1311.4.0 – through 11.4.3 |
Weakness: CWE-862 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
References
- MMSA-2026-00627 vendor-advisory