CVE-2021-20181

Se encontró un fallo de condición de carrera en la implementación del servidor 9pfs de QEMU versiones hasta 5.2.0 incluyéndola. Este fallo permite a un cliente 9p malicioso causar un error de uso de la memoria previamente liberada, escalando potencialmente sus privilegios en el sistema. La mayor amenaza de esta vulnerabilidad es la confidencialidad, la integridad así como la disponibilidad del sistema

This vulnerability allows local attackers to execute arbitrary code on affected installations of QEMU. An attacker must first obtain the ability to execute high-privileged code on the target guest system in order to exploit this vulnerability.
The specific flaw exists within the handling of file descriptor maps. The issue results from the lack of proper locking when performing operations on an object. An attacker can leverage this vulnerability to escalate privileges and execute code in the context of the hypervisor.

It was discovered that QEMU incorrectly handled memory in iSCSI emulation. An attacker inside the guest could possibly use this issue to obtain sensitive information. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. Alexander Bulekov discovered that QEMU incorrectly handled Intel e1000e emulation. An attacker inside the guest could use this issue to cause QEMU to crash, resulting in a denial of service. Various other issues were also addressed.