The M2M Broker in OSEHRA VistA, as distributed before September 30, 2013, allows attackers to bypass authentication and authorization to perform doctor-only actions and read or modify patient records via unspecified vectors related to a "logic flaw."
http://www.osehra.org/blog/vista-patch-available-osehra
http://www.osehra.org/blog/m2m-broker-security-patch
http://www.darkreading.com/vulnerability/anatomy-of-an-electronic-health-record-e/240164441/