CVE-2026-26304: Mattermost fails to verify run_create permission for empty playbookId

March 16, 2026 (updated March 20, 2026)

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2 fail to verify run_create permission for empty playbookId, which allows team members to create unauthorized runs via the playbook run API. Mattermost Advisory ID: MMSA-2025-00542

References

github.com/advisories/GHSA-4pmx-622h-x359
github.com/mattermost/mattermost-plugin-playbooks
github.com/mattermost/mattermost-plugin-playbooks/commit/705f54a818410f3612df3865bfde608ed471037e
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2026-26304

Code Behaviors & Features

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