This indicates an attack attempt to exploit a Denial Of Service Vulnerability in Samba.
The vulnerability is due to an error in the vulnerable application when handling a maliciously crafted request. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system.
Samba Team Samba 4.0.0 through 4.4.x
Samba Team Samba 4.5.x prior to 4.5.16
Samba Team Samba 4.6.x prior to 4.6.14
Samba Team Samba 4.7.x prior to 4.7.6
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor: