CVE-2021-31440

Esta vulnerabilidad permite a atacantes locales escalar los privilegios en las instalaciones afectadas de Linux Kernel versión 5.11.15. Un atacante primero debe obtener la capacidad de ejecutar código poco privilegiado en el sistema de destino para explotar esta vulnerabilidad. El fallo específico se presenta dentro del manejo de los programas eBPF. El problema es debido a una falta de validación apropiada de los programas eBPF suministrados por el usuario antes de ejecutarlos. Un atacante puede explotar esta vulnerabilidad para escalar privilegios y ejecutar código arbitrario en el contexto del kernel. Fue ZDI-CAN-13661

An out-of-bounds access flaw was found in the Linux kernel’s implementation of the eBPF code verifier, where an incorrect register bounds calculation while checking unsigned 32-bit instructions in an eBPF program occurs.. By default accessing the eBPF verifier is only accessible to privileged users with CAP_SYS_ADMIN. The issue results from the lack of proper validation of user-supplied eBPF programs prior to executing them. A local user could use this flaw to crash the system or possibly escalate their privileges on the system.

This vulnerability allows local attackers to escalate privileges on affected installations of Linux Kernel. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.
The specific flaw exists within the handling of eBPF programs. The issue results from the lack of proper validation of user-supplied eBPF programs prior to executing them. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the kernel.