Format string vulnerability in Screen Sharing Server in Apple Mac OS X before 10.9 and Apple Remote Desktop before 3.5.4 allows remote attackers to execute arbitrary code via format string specifiers in a VNC username.

Apple Remote Desktop before 3.7 does not properly use server authentication-type information during decisions about whether to present an unencrypted-connection warning message, which allows remote attackers to obtain sensitive information in opportunistic circumstances by sniffing the network during an unintended cleartext VNC session.