samba: three vulnerabilities

CVE-2016-2123: Trend Micro's Zero Day Initiative and Frederic Besler discovered that the routine ndr_pull_dnsp_name, used to parse data from the Samba Active Directory ldb database, contains an integer overflow flaw, leading to an attacker-controlled memory overwrite. An authenticated user can take advantage of this flaw for remote privilege escalation.

CVE-2016-2125: Simo Sorce of Red Hat discovered that the Samba client code always requests a forwardable ticket when using Kerberos authentication. A target server, which must be in the current or trusted domain/realm, is given a valid general purpose Kerberos "Ticket Granting Ticket" (TGT), which can be used to fully impersonate the authenticated user or service.

CVE-2016-2126: Volker Lendecke discovered several flaws in the Kerberos PAC validation. A remote, authenticated, attacker can cause the winbindd process to crash using a legitimate Kerberos ticket due to incorrect handling of the PAC checksum. A local service with access to the winbindd privileged pipe can cause winbindd to cache elevated access permissions.