Samba version 4.0.0 up to 4.5.2 is vulnerable to privilege elevation due to incorrect handling of the PAC (Privilege Attribute Certificate) checksum. A remote, authenticated, attacker can cause the winbindd process to crash using a legitimate Kerberos ticket. A local service with access to the winbindd privileged pipe can cause winbindd to cache elevated access permissions.

Affected: Ubuntu:14.04:LTS: samba, Ubuntu:16.04:LTS: samba

Frederic Besler and others discovered that the ndr_pull_dnsp_nam function in Samba contained an integer overflow. An authenticated attacker could use this to gain administrative privileges. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, and Ubuntu 16.10. (CVE-2016-2123)

Simo Sorce discovered that that Samba clients always requested a forwardable ticket when using Kerberos authentication. An attacker could use this to impersonate an authenticated user or service. (CVE-2016-2125)

Volker Lendecke discovered that Kerberos PAC validation implementation in Samba contained multiple vulnerabilities. An authenticated attacker could use this to cause a denial of service or gain administrative privileges. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, and Ubuntu 16.10. (CVE-2016-2126)