free5gc UDM provides Unified Data Management (UDM) for free5GC, an open-source project for 5th generation (5G) mobile core networks. Versions up to and including 1.4.1 have a NULL Pointer Dereference vulnerability. Remote unauthenticated attackers can trigger a service panic (Denial of Service) by sending a crafted PUT request with an unexpected ueId, crashing the UDM service. All deployments of free5GC using the UDM component may be affected. free5gc/udm pull request 76 contains a fix for the issue. No direct workaround is available at the application level. Applying the official patch is recommended.