Samba’s WINS server, when acting as an Active Directory Domain Controller, fails to validate certain request types, causing a NULL pointer dereference that crashes the service when an attacker sends crafted UDP packets. This flaw allows an unauthenticated remote attacker to disrupt the availability of the WINS service and, consequently, the domain controller’s name‑resolution functionality. The weakness is a classic NULL pointer dereference identified as CWE‑476.

The vulnerability affects Red Hat Enterprise Linux distributions 6 through 10 and the OpenShift Container Platform 4 when Samba is installed and configured to provide WINS service for Active Directory Domain Controllers. Any system running those distributions with the affected Samba version is vulnerable.

The CVSS score of 7.5 indicates a high‑severity problem. EPSS data are not available, but the flaw is exploitable by an unauthenticated remote attacker who can send UDP packets to the WINS port on an exposed network. The issue is not listed in CISA’s KEV catalog, but its impact on identity‑resolution services makes it a significant availability threat. The attack requires only network access and no privileged credentials, so the risk remains substantial.