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GHSA-rp4v-qc77-phm4

Mattermost doesn't restrict role_updated websocket event broadcasts to members of the affected team or channel

Source: GitHub Advisory Database (reviewed) Moderate CVE-2026-3433

Packages

EcosystemPackageAffectedFixed 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, < 11.5.5 11.5.5
Go github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.17 10.11.17
Go github.com/mattermost/mattermost/server/v8 >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260504071740-9408b98025d7 8.0.0-20260504071740-9408b98025d7

Details

As written in the advisory (Markdown source, shown as plain text).

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to restrict role_updated websocket event broadcasts to members of the affected team or channel, which allows an authenticated attacker with guest-level access to observe permission scheme change notifications for private teams they are not a member of via the websocket connection. Mattermost Advisory ID: MMSA-2026-00616

References

External links from the advisory. They lead to third-party sites.