CVE-2026-3637
Medium
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
SeverityMedium
CVSS4.3
Exploit probability—
Product
Mattermost Server
PublishedMay 18, 2026
First seenMay 18, 2026
Weakness typeCWE-862Missing authorization
How to fix
Update
- mattermost mattermost_server10.11.14, 11.4.4, 11.5.2 or later
- github.com/mattermost/mattermost/server/v810.11.14, 11.4.4, 8.0.0-20260316171743-090408f09f53, 11.5.2 or later
- github.com/mattermost/mattermost-server5.3.2-0.20260316171743-090408f09f53, 10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatible or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 10.11.0 ≤ v < 10.11.14, 11.4.0 ≤ v < 11.4.4, 11.5.0 ≤ v < 11.5.2 | 10.11.14, 11.4.4, 11.5.2 |
| github.com/mattermost/mattermost/server/v8Go | 10.11.0 ≤ v < 10.11.14, 11.4.0 ≤ v < 11.4.4, v < 8.0.0-20260316171743-090408f09f53, 11.5.0 ≤ v < 11.5.2 | 10.11.14, 11.4.4, 8.0.0-20260316171743-090408f09f53, 11.5.2 |
| github.com/mattermost/mattermost-serverGo | v < 5.3.2-0.20260316171743-090408f09f53, 10.11.0+incompatible ≤ v < 10.11.14+incompatible, 11.4.0+incompatible ≤ v < 11.4.4+incompatible, 11.5.0+incompatible ≤ v < 11.5.2+incompatible | 5.3.2-0.20260316171743-090408f09f53, 10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatible |
| github.com/mattermost/mattermost-server/v5Go | No range specified | — |
| github.com/mattermost/mattermost-server/v6Go | No range specified | — |
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