The security researcher Manfred Paul of the RedRocket CTF team released the exploit code for a high-severity privilege escalation bug, tracked as CVE-2021-3490, in Linux kernel eBPF (Extended Berkeley Packet Filter). A local attacker could exploit the flaw to escalate privileges on Ubuntu machines.
Extended Berkeley Packet Filter (eBPF) is a kernel technology (starting in Linux 4.x) that allows programs to run without having to change the kernel source code or adding additional modules. It is a sort of lightweight, sandbox virtual machine (VM) inside the Linux kernel, where programmers can run BPF bytecode that takes advantage of specific kernel resources.
Paul reported the bug in May through Trend Micro’s Zero Day Initiative, he demonstrated that user-supplied programs are not properly validated before being executed.
The security researcher Valentina Palmiotti published a blog post that contains technical details about the flaw along with the exploit code that works on fresh installs of both Ubuntu 20.10 and 21.04
She demonstrates how to exploit the issue to trigger a DoS condition of escalate privileges.
Below is a video PoC for the CVE-2021-3490 vulnerability on Ubuntu 21.04 published by the researcher:
(SecurityAffairs – hacking, Linux)