QEMU (aka Quick Emulator) built with the TPR optimization for 32-bit Windows guests support is vulnerable to a null pointer dereference flaw. It occurs while doing I/O port write operations via hmp interface. In that, 'current_cpu' remains null, which leads to the null pointer dereference. A user or process could use this flaw to crash the QEMU instance, resulting in DoS issue.
https://security.gentoo.org/glsa/201604-01
https://lists.gnu.org/archive/html/qemu-devel/2016-01/msg02812.html
https://bugzilla.redhat.com/show_bug.cgi?id=1283934
http://www.securityfocus.com/bid/81058
http://www.openwall.com/lists/oss-security/2016/01/16/6
http://www.openwall.com/lists/oss-security/2016/01/16/1
http://www.debian.org/security/2016/dsa-3471