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GeoServer Host Header Injection to SSRF (CVE-2021-40822)

cve-2021 | Level: Easy  | Total Lab Runs: 0 | Premium Lab

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What is GeoServer?

GeoServer is an open source software server written in Java that allows users to share and edit geospatial data. Designed for interoperability, it publishes data from any major spatial data source using open standards.


CVE-2021-40822: Geoserver SSRF

In 2021, a researcher by the alias @phor3nsic_br discovered an SSRF vulnerability in Geoserver. It was assigned CVE ID CVE-2021-40822.

As stated on the NVD page for CVE-2021-40822:

GeoServer through 2.18.5 and 2.19.x through 2.19.2 allows SSRF via the option for setting a proxy host.

The base score assigned to this vulnerability was 7.5 (HIGH).

In this lab, we will learn how to leverage the Host Header Injection to perform an SSRF attack in the GeoServer application (CVE-2021-40822) and interact with an internal web server running on the target server.

Lab Environment

In this lab environment, the user is going to get access to a Kali GUI instance. A vulnerable instance of the GeoServer application is hosted on the target server. It can be accessed using the tools installed on Kali at http://demo.ine.local:8080/geoserver.

Objective: Leverage the SSRF vulnerability in the GeoServer application to interact with the internal HTTP server running on port 8000 and retrieve the flag.


The setup 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.2. Run "ip addr" to know the values of X and Y.

  • The target GeoServer application should be accessible on http://demo.ine.local:8000/geoserver

  • 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.

Technical Support for this Lab:

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