CVE-2026-3433Medium· 4.3▾ SunlitMattermost doesn't restrict role_updated websocket event broadcasts to members of the affected team or channel
▾ Sunlit zone — Low / medium · no exploitation signal
impact 23.7 · likelihood 0 · exploitation 0
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Exploit-prediction probability, daily snapshots since Aug 25.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
Last analysed / modified upstream
0.2%
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
github.com/mattermost/mattermost-server >= 11.6.0, < 11.6.1github.com/mattermost/mattermost-server >= 11.5.0, < 11.5.5github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.17github.com/mattermost/mattermost/server/v8 >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260504071740-9408b98025d7Upgrade to a patched release:
github.com/mattermost/mattermost-server 11.6.1github.com/mattermost/mattermost-server 11.5.5github.com/mattermost/mattermost-server 10.11.17github.com/mattermost/mattermost/server/v8 8.0.0-20260504071740-9408b98025d7Connected by shared product, vendor, weakness, or advisory.
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