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. It was found that certain Samba configurations did not enforce the password lockout mechanism. A remote attacker could use this flaw to perform password guessing attacks on Samba user accounts. Note: this flaw only affected Samba when deployed as a Primary Domain Controller. A flaw was found in the way the pam_winbind module handled configurations that specified a non-existent group as required. An authenticated user could possibly use this flaw to gain access to a service using pam_winbind in its PAM configuration when group restriction was intended for access to the service. Red Hat would like to thank the Samba project for reporting CVE-2013-4496 and Sam Richardson for reporting CVE-2012-6150. Upstream acknowledges Andrew Bartlett as the original reporter of CVE-2013-4496. All users of Samba are advised to upgrade to these updated packages, which contain backported patches to correct these issues. After installing this update, the smb service will be restarted automatically.