CVE-2016-9603

Se ha detectado una vulnerabilidad de desbordamiento de búfer basado en memoria dinámica (heap) en el soporte del controlador de pantalla VNC del emulador Cirrus CLGD 54xx VGA de QEMU en versiones anteriores a la 2.9. El problema podía ocurrir cuando un cliente VNC intentaba actualizar su pantalla después de que un invitado realizara una operación VGA. Un usuario/proceso privilegiado dentro de un guest podría usar esta vulnerabilidad para provocar que el proceso de QEMU se cierre inesperadamente o, potencialmente, ejecutar código arbitrario en el host con privilegios del proceso de QEMU.

A heap buffer overflow flaw was found in QEMU's Cirrus CLGD 54xx VGA emulator's VNC display driver support; the issue could occur when a VNC client attempted to update its display after a VGA operation is performed by a guest. A privileged user/process inside a guest could use this flaw to crash the QEMU process or, potentially, execute arbitrary code on the host with privileges of the QEMU process.

An update that solves four vulnerabilities and has three fixes is now available. This update for xen fixes several security issues. Allowing for all of privilege escalation, host crashes, and information leaks by placing a IRET hypercall in the middle of a multicall batch allowing for all of privilege escalation, host crashes, and information leaks because of a missing check when transfering pages via GNTTABOP_transfer. Hw/display/cirrus_vga_rop.h allowed local guest OS privileged users to cause a denial of service (out-of-bounds read and QEMU process crash) via vectors related to copying VGA data via the cirrus_bitblt_rop_fwd_transp_ and cirrus_bitblt_rop_fwd_ functions. A privileged user within the guest VM could have caused a heap overflow in the device model process, potentially escalating their privileges to that of the device model process.