Proof of Concept (PoC) CVE-2021-4034

Overview

PwnKit-Exploit

CVE-2021-4034

PolKit

@c0br40x help to make this section in README!!

Proof of Concept

Proof of Concept

[email protected]:~/PwnKit-Exploit$ make
cc -Wall    exploit.c   -o exploit
[email protected]:~/PwnKit-Exploit$ whoami
debian
[email protected]:~/PwnKit-Exploit$ ./exploit
Current User before execute exploit
[email protected]$whoami: debian
Exploit written by @luijait (0x6c75696a616974)
[+] Enjoy your root if exploit was completed succesfully
[email protected]:/home/debian/PwnKit-Exploit# whoami
root
[email protected]:/home/debian/PwnKit-Exploit# 

Fix

Command Use
sudo chmod 0755 pkexec Fix CVE 2021-4034

Installation & Use

git clone https://github.com/luijait/PwnKit-Exploit

cd PwnKit-Exploit

make

./exploit

whoami

Command Utility
make clean Clean build to test code modified

Explanation

Based blog.qualys.com

The beginning of pkexec’s main() function processes the command-line arguments (lines 534-568), and searches for the program to be executed, if its path is not absolute, in the directories of the PATH environment variable (lines 610-640):

435 main (int argc, char *argv[])
436 {
...
534   for (n = 1; n < (guint) argc; n++)
535     {
...
568     }
...
610   path = g_strdup (argv[n]);
...
629   if (path[0] != '/')
630     {
...
632       s = g_find_program_in_path (path);
...
639       argv[n] = path = s;
640     }

unfortunately, if the number of command-line arguments argc is 0 – which means if the argument list argv that we pass to execve() is empty, i.e. {NULL} – then argv[0] is NULL. This is the argument list’s terminator. Therefore:

at line 534, the integer n is permanently set to 1; at line 610, the pointer path is read out-of-bounds from argv[1]; at line 639, the pointer s is written out-of-bounds to argv[1]. But what exactly is read from and written to this out-of-bounds argv[1]?

To answer this question, we must digress briefly. When we execve() a new program, the kernel copies our argument, environment strings, and pointers (argv and envp) to the end of the new program’s stack; for example:

|---------+---------+-----+------------|---------+---------+-----+------------| 
| argv[0] | argv[1] | ... | argv[argc] | envp[0] | envp[1] | ... | envp[envc] | 
|----|----+----|----+-----+-----|------|----|----+----|----+-----+-----|------| 
V         V                V           V         V                V 

"program" "-option"           NULL      "value" "PATH=name"          NULL 

Clearly, because the argv and envp pointers are contiguous in memory, if argc is 0, then the out-of-bounds argv[1] is actually envp[0], the pointer to our first environment variable, “value”. Consequently:

At line 610, the path of the program to be executed is read out-of-bounds from argv[1] (i.e. envp[0]), and points to “value”; At line 632, this path “value” is passed to g_find_program_in_path() (because “value” does not start with a slash, at line 629); Then, g_find_program_in_path() searches for an executable file named “value” in the directories of our PATH environment variable; If such an executable file is found, its full path is returned to pkexec’s main() function (at line 632); Finally, at line 639, this full path is written out-of-bounds to argv[1] (i.e. envp[0]), thus overwriting our first environment variable. So, stated more precisely:

If our PATH environment variable is “PATH=name”, and if the directory “name” exists (in the current working directory) and contains an executable file named “value”, then a pointer to the string “name/value” is written out-of-bounds to envp[0]; OR

If our PATH is “PATH=name=.”, and if the directory “name=.” exists and contains an executable file named “value”, then a pointer to the string “name=./value” is written out-of-bounds to envp[0]. In other words, this out-of-bounds write allows us to re-introduce an “unsecure” environment variable (for example, LD_PRELOAD) into pkexec’s environment. These “unsecure” variables are normally removed (by ld.so) from the environment of SUID programs before the main() function is called. We will exploit this powerful primitive in the following section.

Last-minute note: polkit also supports non-Linux operating systems such as Solaris and *BSD, but we have not investigated their exploitability. However, we note that OpenBSD is not exploitable, because its kernel refuses to execve() a program if argc is 0.

You might also like...
An exploit for CVE-2021-4034 aka Pwnkit: Local Privilege Escalation in polkit's pkexec

CVE-2021-4034 Exploit Usage $ git clone https://github.com/whokilleddb/CVE-2021-4034 $ cd CVE-2021-4034 $ make [!] CVE-2021-4034 Exploit By whokilledd

PoC for CVE-2021-28476 a guest-to-host
PoC for CVE-2021-28476 a guest-to-host "Hyper-V Remote Code Execution Vulnerability" in vmswitch.sys.

CVE-2021-28476: a guest-to-host "Microsoft Hyper-V Remote Code Execution Vulnerability" in vmswitch.sys. This is a proof of concept for CVE-2021-28476

PoC (DoS) for CVE-2021-40449 - Win32k Elevation of Privilege Vulnerability (LPE)
PoC (DoS) for CVE-2021-40449 - Win32k Elevation of Privilege Vulnerability (LPE)

CallbackHell DoS PoC for CVE-2021-40449 (Win32k - LPE) CallbackHell Description Technical Writeup PoC References Description CVE-2021-40449 is a use-a

Plex media server local privilige escalation poc - CVE-2021-42835

Local Privilege PlEXcalasion - CVE-2021-42835 Plex Media Server for Windows prior to version 1.25.0.5282, vulnerable to Time Of Check Time Of Use (TOC

CVE-2021-3156 POC and Docker and Analysis write up

CVE-2021-3156 [toc] 漏洞简介 漏洞编号: CVE-2021-3156 漏洞产品: sudo 影响版本: 1.8.2-1.8.31sp12; 1.9.0-1.9.5sp1 利用后果: 本地提权 源码获取: https://www.sudo.ws/getting/source/ 环境

A refactored Proof-of-concept originally developed in 2017 to print all function calls with their arguments data types and values using Ptrace during program execution.

print-function-args-debugger A refactored Proof-of-concept originally developed in 2017 to print all function calls with their arguments data types an

Proof-of-concept implementation for the paper "Osiris: Automated Discovery of Microarchitectural Side Channels" (USENIX Security'21)

Osiris This repository contains the implementation of the Osiris framework discussed in the research paper "Osiris: Automated Discovery of Microarchit

Proof of concept Beacon Object File (BOF) that attempts to detect userland hooks in place by AV/EDR

Detect-Hooks Detect-Hooks is a proof of concept Beacon Object File (BOF) that attempts to detect userland API hooks in place by AV/EDR. The BOF will r

Owner
Luis Javier
Pentester | Red Teamer | CCNA3 | Exploit Dev
Luis Javier
Proof of Concept for CVE-2021-1585: Cisco ASA Device Manager RCE

staystaystay staystaystay is a proof of concept exploit for CVE-2021-1585, a man in the middle or evil endpoint RCE issue affecting Cisco ASA Device M

Jake Baines 9 Sep 28, 2022
PoC for PwnKit: Local Privilege Escalation Vulnerability in polkit’s pkexec (CVE-2021-4034)

CVE-2021-4034 PoC for PwnKit: Local Privilege Escalation Vulnerability in polkit’s pkexec (CVE-2021-4034) https://seclists.org/oss-sec/2022/q1/80 http

Andris Raugulis 924 Nov 21, 2022
CVE-2021-4034 POC and Docker and Analysis write up

CVE-2021-4034 POC and Docker and Analysis write up

breeze 9 Oct 22, 2022
PoC for cve-2021-4034

cve-2021-4034 PoC for cve-2021-4034 Based on the PoC by https://haxx.in: https://haxx.in/files/blasty-vs-pkexec.c. Probably he's https://github.com/bl

Michael Schmid 3 Jun 19, 2022
CVE-2021-4034 One day for the polkit privilege escalation exploit

CVE-2021-4034 One day for the polkit privilege escalation exploit Just execute make, ./cve-2021-4034 and enjoy your root shell. The original advisory

Davide Berardi 1.7k Nov 26, 2022
Self-contained exploit for CVE-2021-4034 - Pkexec Local Privilege Escalation

PwnKit Self-contained exploit for CVE-2021-4034 - Pkexec Local Privilege Escalation Usage Should work out of the box on Linux distributions based on U

Oliver Lyak 679 Nov 25, 2022
This repository contains an exploit of CVE-2021-4034, a local privilege escalation in pkexec

pwnkit (CVE-2021-4034) Privilege Escalation exploit sample This repository contains an exploit of CVE-2021-4034, a local privilege escalation in pkexe

Peter Gottesman 28 Nov 6, 2022
CVE-2021-4034 Add Root User - Pkexec Local Privilege Escalation

CVE-2021-4034 CVE-2021-4034 Add Root User - Pkexec Local Privilege Escalation 根据CVE-2021-4034进行了加强,执行Exploit将会默认添加用户名rooter,密码[email protected],并且rooter用户将具

倾旋 88 Oct 16, 2022
Pre-compiled builds for CVE-2021-4034

CVE-2021-4034 Precompiled builds for CVE-2021-4034. Of course you shouldn't trust precompiled builds :) This release works slightly different: first a

null 11 Nov 9, 2022