This indicates an attack attempt against an Information Disclosure vulnerability in Samba.
The vulnerability is caused by an error when the vulnerable software handles a specially crafted request. A remote attacker can exploit this to gain unauthorized access to sensitive information.
Samba Team Samba 4.4.x prior to 4.4.16
Samba Team Samba 4.5.x prior to 4.5.14
Samba Team Samba 4.6.x prior to 4.6.8
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Apply the most recent upgrade or patch from the vendor.