Multiple use-after-free vulnerabilities in vnc.c in the VNC server in QEMU 0.10.6 and earlier might allow guest OS users to execute arbitrary code on the host OS by establishing a connection from a VNC client and then (1) disconnecting during data transfer, (2) sending a message using incorrect integer data types, or (3) using the Fuzzy Screen Mode protocol, related to double free vulnerabilities.
https://bugzilla.redhat.com/show_bug.cgi?id=508567
https://bugzilla.redhat.com/show_bug.cgi?id=501131
http://www.openwall.com/lists/oss-security/2009/10/16/8
http://www.openwall.com/lists/oss-security/2009/10/16/5