An uninitialized pointer use flaw was found in the Samba daemon (smbd). A malicious Samba client could send specially crafted netlogon packets that, when processed by smbd, could potentially lead to arbitrary code execution with the privileges of the user running smbd (by default, the root user).
This vulnerability was assigned CVE-2015-0240.
From the debian security mailing list :
Richard van Eeden of Microsoft Vulnerability Research discovered that Samba, a SMB/CIFS file, print, and login server for Unix, contains a flaw in the netlogon server code which allows remote code execution with root privileges from an unauthenticated connection
Red Hat rated this flaw as having crititcal impact on RHEL 6 ( samba 3.6) and important impact on RHEL 7 (samba 4.1).
According to Red Hat :
“In Samba 4.1 and above, this crash can only be triggerred after setting ‘server schannel = yes’ in the server configuration”.