A fresh advisory from SAMBA.org:

All versions of Samba from 4.0.0 onwards are vulnerable to a use after
free vulnerability, where a malicious SMB1 request can be used to
control the contents of heap memory via a deallocated heap pointer. It
is possible this may be used to compromise the SMB server.

The major Linux distributions (Red Hat, Ubuntu, Debian) has already rolled out security patches for this vulnerability, tracked as CVE-2017-14746, that affects all versions of SAMBA since 4.0.

According to the project’s advisory, an unauthenticated attacker could send specially-crafted SMB1 requests to cause the server to crash or execute arbitrary code.

Sysadms should to apply the fixes to their server, otherwise another possibility consists in turning off SAMBA 1:


Prevent SMB1 access to the server by setting the parameter:

server min protocol = SMB2

to the [global] section of your smb.conf and restart smbd. This
prevents and SMB1 access to the server. Note this could cause older
clients to be unable to connect to the server.