A recently disclosed vulnerability, tracked as CVE-2023-34059, affects the open-vm-tools package, which is an open-source implementation of VMware Tools. The vulnerability lies within the vmware-user-suid-wrapper component of open-vm-tools, which allows a malicious actor with non-root privileges to hijack the /dev/uinput file descriptor. This hijacking enables the attacker to simulate user inputs, potentially leading to unauthorized access and malicious activities on affected systems.

In this long-read post, we will take an in-depth look at this vulnerability, its exploit details, and the code snippets involved. We will also provide useful links to the original references and relevant resources for further understanding and mitigation of this issue.

Background: Open-VM-Tools and the vmware-user-suid-wrapper component

Open-VM-Tools is an open-source implementation of VMware Tools, a set of utilities and drivers that enhance the performance and functionality of virtual machines running on VMware platforms. The open-vm-tools package is widely used by system administrators and developers for managing and optimizing virtual machines.

The vmware-user-suid-wrapper is a component of the open-vm-tools package designed to manage user input and interaction within a virtual machine. It is typically installed as a setuid binary, allowing it to run with elevated (root) privileges when executed by a non-root user.

Vulnerability Details: File Descriptor Hijacking in /dev/uinput

The vulnerability (CVE-2023-34059) stems from the improper handling of the /dev/uinput file descriptor within the vmware-user-suid-wrapper component. The /dev/uinput file descriptor is used to manage user input devices, such as keyboards and mice, within the virtual machine environment.

When a non-root user runs the vmware-user-suid-wrapper binary, it opens the /dev/uinput file descriptor with appropriate permissions. However, it fails to close the file descriptor upon termination, leaving it open and vulnerable to hijacking by a malicious actor.

Exploit Details: Simulating User Inputs and Potential Consequences

An attacker with non-root privileges on the affected system could exploit this vulnerability by hijacking the open /dev/uinput file descriptor. This hijacking allows the attacker to simulate user inputs, such as keyboard and mouse events, within the virtual machine.

The potential consequences of this exploit are significant, as it may enable the attacker to

1. Bypass authentication mechanisms, gaining unauthorized access to sensitive data and system resources.
2. Manipulate the virtual machine's environment, potentially leading to system compromise, data loss, or disruption of services.
3. Perform keylogging and other malicious activities to collect sensitive information from unsuspecting users.

Code Snippet: Example of Exploiting the Vulnerability

The following code snippet demonstrates how an attacker could exploit the CVE-2023-34059 vulnerability to hijack the open /dev/uinput file descriptor and simulate user inputs:

#include <fcntl.h>
#include <linux/uinput.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define UINPUT_PATH "/dev/uinput"

int main() {
  // Open the /dev/uinput file descriptor
  int fd = open(UINPUT_PATH, O_WRONLY | O_NONBLOCK);
  if (fd < ) {
    perror("Failed to open /dev/uinput");
    exit(1);
  }

  // Hijack the open file descriptor
  // (Insert malicious code here to simulate user inputs)

  // Close the file descriptor upon completion
  close(fd);
  return ;
}

Original References and Resources

1. CVE-2023-34059 - Vulnerability Details
2. Open-VM-Tools Project Homepage
3. VMware Security Advisory VMSA-2023-0015

Mitigation and Recommendations

Users and administrators should apply the appropriate patches or updates provided by VMware and the open-vm-tools project to address this vulnerability. Additionally, it is essential to follow best practices for securing virtual machine environments, such as implementing strong access controls, regular monitoring, and timely patch management.

Conclusion

CVE-2023-34059 is a significant vulnerability that affects the open-vm-tools package and enables malicious actors with non-root privileges to hijack the /dev/uinput file descriptor and simulate user inputs. Understanding the exploit details, code snippets involved, and potential consequences of this vulnerability is crucial for effectively securing affected systems. Be sure to apply relevant patches and follow recommended security practices to mitigate this vulnerability and protect your virtual machine environments.

Timeline

Published on: 10/27/2023 05:15:39 UTC
Last modified on: 11/27/2023 12:15:07 UTC