It was found that samba before 4.4.16, 4.5.x before 4.5.14, and 4.6.x before 4.6.8 did not enforce "SMB signing" when certain configuration options were enabled. A remote attacker could launch a man-in-the-middle attack and retrieve information in plain-text.
https://www.samba.org/samba/security/CVE-2017-12150.html
https://www.debian.org/security/2017/dsa-3983
https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03817en_us
https://security.netapp.com/advisory/ntap-20170921-0001/
https://h20566.www2.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbns03775en_us
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-12150
https://access.redhat.com/errata/RHSA-2017:2858
https://access.redhat.com/errata/RHSA-2017:2791
https://access.redhat.com/errata/RHSA-2017:2790
https://access.redhat.com/errata/RHSA-2017:2789