GO-2026-5671
Mattermost doesn't validate the Host header when constructing response URLs for custom slash command in github.com/mattermost/mattermost-server
Quick fix
GO-2026-5671 — github.com/mattermost/mattermost-server: upgrade to the fixed version with the command below.
go get github.com/mattermost/mattermost-server@v10.11.14+incompatibleDetails
Mattermost doesn't validate the Host header when constructing response URLs for custom slash command in github.com/mattermost/mattermost-server.
NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions.
(If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.)
The additional affected modules and versions are: github.com/mattermost/mattermost-server/v5 before v5.3.2-0.20260325160634-e738016c5920.
Are you affected?
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Affected packages
10.11.0+incompatibleFixed in: 10.11.14+incompatiblego get github.com/mattermost/mattermost-server@v10.11.14+incompatible0No fixed version published yet for github.com/mattermost/mattermost-server/v5 (go modules). Pin to a known-safe version or switch to an alternative.
0No fixed version published yet for github.com/mattermost/mattermost-server/v6 (go modules). Pin to a known-safe version or switch to an alternative.
0Fixed in: 8.0.0-20260325160634-e738016c5920go get github.com/mattermost/mattermost/server/v8@v8.0.0-20260325160634-e738016c5920