Virtual Network Computing (VNC) is a remote display system which allows you to view a computer's desktop environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures. TigerVNC is a suite of VNC servers and clients.
It was discovered that vncviewer could prompt for and send authentication credentials to a remote server without first properly validating the server's X.509 certificate. As vncviewer did not indicate that the certificate was bad or missing, a man-in-the-middle attacker could use this flaw to trick a vncviewer client into connecting to a spoofed VNC server, allowing the attacker to obtain the client's credentials. (CVE-2011-1775)
All tigervnc users should upgrade to these updated packages, which contain a backported patch to correct this issue.