This indicates an attack attempt to exploit a Code Execution vulnerability in Samba.
The vulnerability is due to an error in smbd when handling files uploaded to writable share. A remote attacker may be able to exploit this to execute arbitrary code on the affected machine.
Samba 3.5.0 to 4.6.3, 4.5.9 and 4.4.13
System Compromise: Remote attackers can gain control of vulnerable systems
Apply the most recent upgrade or patch from the vendor