GHSA-5gmf-x7hg-97wf
Mattermost doesn't filter nil elements from outgoing webhook attachment payloads before processing
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 | < 8.0.0-20260407102538-faa7d75b4ea0 | 8.0.0-20260407102538-faa7d75b4ea0 |
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 filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry. Mattermost Advisory ID: MMSA-2026-00641
References
External links from the advisory. They lead to third-party sites.