CVE-2017-15118

Se ha detectado una vulnerabilidad de desbordamiento de búfer basado en pila en la implementación de servidor NBD en qemu en versiones anteriores a la 2.11, permitiendo a un cliente solicitar un nombre de exportación de hasta 4096 bytes, que de hecho debería estar limitado a 256 bytes, provocando una escritura de pila fuera de límites en el proceso qemu. Si el servidor NBD requiere TLS, el atacante no puede activar el desbordamiento del búfer sin haber negociado primero con éxito el TLS.

A stack-based buffer overflow vulnerability was found in NBD server implementation in qemu allowing a client to request an export name of size up to 4096 bytes, which in fact should be limited to 256 bytes, allowing causing an out-of-bounds stack write in the qemu process. If NBD server requires TLS, the attacker cannot trigger the buffer overflow without first successfully negotiating TLS.

USN-3575-1 fixed vulnerabilities in QEMU. The fix for CVE-2017-11334 caused a regression in Xen environments. This update removes the problematic fix pending further investigation. It was discovered that QEMU incorrectly handled guest ram. A privileged attacker inside the guest could use this issue to cause QEMU to crash, resulting in a denial of service. This issue only affected Ubuntu 14.04 LTS and Ubuntu 16.04 LTS. David Buchanan discovered that QEMU incorrectly handled the VGA device. A privileged attacker inside the guest could use this issue to cause QEMU to crash, resulting in a denial of service. This issue was only addressed in Ubuntu 17.10. Thomas Garnier discovered that QEMU incorrectly handled multiboot. An attacker could use this issue to cause QEMU to crash, resulting in a denial of service, or possibly execute arbitrary code on the host. In the default installation, when QEMU is used with libvirt, attackers would be isolated by the libvirt AppArmor profile. This issue only affected Ubuntu 14.04 LTS and Ubuntu 16.04 LTS. Various other issues were also addressed.