CVE-2025-49222 – Mattermost Shared Channel Upload Type Validation Bypass

https://notcve.org/view.php?id=CVE-2025-49222

21 Aug 2025 — Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.9.x <= 10.9.2, 10.10.x <= 10.10.0 fail to validate upload types in remote cluster upload sessions which allows a system admin to upload non-attachment file types via shared channels that could potentially be placed in arbitrary filesystem directories. • https://mattermost.com/security-updates • CWE-434: Unrestricted Upload of File with Dangerous Type •