Red Hat Security Advisory 2016-1487-01 – Samba is an open-source implementation of the Server Message Block or Common Internet File System protocol, which allows PC-compatible machines to share files, printers, and other information. Security Fix: A flaw was found in the way Samba initiated signed DCE/RPC connections. A man-in-the-middle attacker could use this flaw to downgrade the connection to not use signing and therefore impersonate the server.