CVE-2026-16046: Missing run-state validation on finished playbook runs

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-17 · updated 2026-08-18
Weakness: CWE-863

Description

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to enforce run-state validation on write operations for finished playbook runs which allows a run participant to modify status, checklists, retrospective content, ownership, and participants on completed runs via REST and GraphQL API requests. Mattermost Advisory ID: MMSA-2026-00675

Affected products

Mattermost: from 10.11.0 before 10.11.22; from 11.7.0 before 11.7.7 — fixed in 10.11.22, 11.7.7

How to fix

Upgrade to a fixed version: Mattermost 10.11.22, 11.7.7. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

Get alerted when CVE-2026-16046 or the next vulnerability affects your stack