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Xstream Deserialization RCE (CVE-2021-21351)
cve-2021 | Level: Easy | Total Lab Runs: 0 | Premium Lab |
What is Xstream?
XStream is a simple library to serialize objects to XML and back again.
What is CVE-2021-21351?
XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.16, there is a vulnerability that may allow a remote attacker to load and execute arbitrary code from a remote host only by manipulating the processed input stream. No user is affected, who followed the recommendation to set up XStream's security framework with a whitelist limited to the minimal required types. If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.16.
According to NVD, this vulnerability was critical, with a base score of 9.1.
In this lab, we will learn to exploit a severe, arbitrary code execution vulnerability (CVE-2021-21351) in the Xtream library by sending a malicious XML payload.
In this lab environment, the user is going to get access to an Ubuntu TTYD instance. A vulnerable instance of an application using the Xstream library is hosted on the provided machine. It can be accessed using the tools installed on Ubuntu at http://127.0.0.1:8080.
Objective: Leverage the affected version of Xstream to elevate your privileges and retrieve the flag from the /root directory.
The setup code is based on the following Github repository:
This lab is dedicated to you! No other users are on this network :)
Once you start the lab, you will have access to a root terminal of a Kali instance
Your Kali has an interface with IP address 192.X.Y.Z. Run "ip addr" to know the values of X and Y.
The target application should be located on the same IP address on port 8080.
The JNDI Injection Exploit JAR is available in the home directory of the user accessible in the Ubuntu instance.
Do not attack the gateway located at IP address 192.X.Y.1
The following activities are strictly prohibited on this website unless otherwise explicitly stated as allowed in the mission statement:
- Using automated scanners
- Using brute force attacks
- Denial of Service attacks
- Attacking other student machines in challenges where you might achieve a shell on the vulnerable system
- Attacking the lab infrastructure
Users violating the above will be either temporarily or permanently banned from the website.
If you are unsure about an activity, then please contact support to confirm that it is allowed on our website.
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