Mattermost versions 9.5.x <= 9.5.3, 9.6.x <= 9.6.1, 8.1.x <= 8.1.12 fail to enforce proper access controls for channel and team membership when linking a playbook run to a channel which allows members to link their runs to private channels they were not members of.
Severity
CVSS 3.1
5.9 medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N
EPSS
0.2% chance of exploitation in the next 30 days; higher than 13% of CVEs (scores of 2026-10-31)