CVE-2026-8823: User Manager can demote bot accounts to guest without bot-management permission

Severity: low (CVSS 3.8 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: 2026-06-22 · updated 2026-06-26
Weakness: CWE-863

Description

Mattermost versions 11.7.x <= 11.7.0, 10.11.x <= 10.11.17 fail to validate bot targets when demoting users to guests which allows a lower-privileged administrator to degrade arbitrary bot accounts via the standard demote-user API.. Mattermost Advisory ID: MMSA-2026-00669

Affected products

Mattermost: from 10.11.0 before 10.11.18; from 11.7.0 before 11.7.1 — fixed in 10.11.18, 11.7.1

How to fix

Upgrade to a fixed version: Mattermost 10.11.18, 11.7.1. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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