GHSA-w9m8-p4cc-4qj9
Mattermost doesn't properly validate msgpack-encoded WebSocket frames before memory allocation
Packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | >= 11.6.0, < 11.6.1 | 11.6.1 |
| Go | github.com/mattermost/mattermost-server | >= 11.5.0, < 11.5.4 | 11.5.4 |
| Go | github.com/mattermost/mattermost-server | >= 11.4.0, < 11.4.5 | 11.4.5 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0, < 10.11.15 | 10.11.15 |
| Go | github.com/mattermost/mattermost/server/v8 | < 8.0.0-20260410202636-17939826efa2 | 8.0.0-20260410202636-17939826efa2 |
Details
As written in the advisory (Markdown source, shown as plain text).
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 properly validate msgpack-encoded WebSocket frames before memory allocation which allows an unauthenticated remote attacker to crash the server process and cause a full service outage for all users via a crafted binary WebSocket message sent to the public WebSocket endpoint.. Mattermost Advisory ID: MMSA-2026-00647
References
External links from the advisory. They lead to third-party sites.