This indicates an attempt to exploit a boundry error vulnerability in Samba server.
The vulnerability is caused by a boundary error in the "send_mailslot()" function. It can be exploited via a GETDC mailslot request following an offset username in a SAMLOGON logon request. Successful exploitation requires that the "domain logons" option is enabled. As a result of exploiting this, remote attackers can cause a denial of service or execute arbitrary code.
Denial of service.
System Compromise: Remote attackers can gain control of vulnerable systems.
Update to version 3.0.28 or apply patch.