Multiple vulnerabilities have been found in Qemu. Multiple heap-based buffer overflows in the cirrus_invalidate_region function in the Cirrus VGA extension in QEMU 0.8.2, as used in Xen and possibly other products, might allow local users to execute arbitrary code via unspecified vectors related to attempting to mark non-existent regions as dirty, aka the bitblt heap overflow. Integer signedness error in the NE2000 emulator in QEMU 0.8.2, as used in Xen and possibly other products, allows local users to trigger a heap-based buffer overflow via certain register values that bypass sanity checks, aka QEMU NE2000 receive integer signedness error. QEMU 0.8.2 allows local users to halt a virtual machine by executing the icebp instruction. QEMU 0.8.2 allows local users to crash a virtual machine via the divisor operand to the aam instruction, as demonstrated by aam 0x0, which triggers a divide-by-zero error. The NE2000 emulator in QEMU 0.8.2 allows local users to execute arbitrary code by writing Ethernet frames with a size larger than the MTU to the EN0_TCNT register, which triggers a heap-based buffer overflow in the slirp library, aka NE2000 mtu heap overflow. Heap-based buffer overflow in QEMU 0.8.2, as used in Xen and possibly other products, allows local users to execute arbitrary code via crafted data in the net socket listen option, aka QEMU net socket heap overflow. QEMU 0.9.0 allows local users of a Windows XP SP2 guest operating system to overwrite the TranslationBlock buffer, and probably have unspecified other impacts related to an overflow, via certain Windows executable programs, as demonstrated by qemu-dos.com. Qemu 0.9.1 and earlier does not perform range checks for block device read or write requests, which allows guest host users with root privileges to access arbitrary memory and escape the virtual machine. Changing removable media in QEMU could trigger a bug similar to CVE-2008-2004, which would allow local guest users to read arbitrary files on the host by modifying the header of the image to identify a different format. See the diskformat: parameter to the -usbdevice option. The drive_init function in QEMU 0.9.1 determines the format of a raw disk image based on the header, which allows local guest users to read arbitrary files on the host by modifying the header to identify a different format, which is used when the guest is restarted. See the -format option. The updated packages have been patched to fix these issues.