diff --git a/backend/app/routers/kiosk.py b/backend/app/routers/kiosk.py
index 3f5504c..cd52dc0 100644
--- a/backend/app/routers/kiosk.py
+++ b/backend/app/routers/kiosk.py
@@ -172,6 +172,7 @@ async def kiosk_login_nfc(
     """NFC-Login: NFC-UID der Karte."""
     user, session_token = await kiosk_auth_service.login_nfc(
         nfc_uid=data.nfc_uid,
+        pin=data.pin,
         company_id=device.company_id,
         device_id=device.id,
         db=db,
diff --git a/backend/app/routers/users.py b/backend/app/routers/users.py
index b493914..727257f 100644
--- a/backend/app/routers/users.py
+++ b/backend/app/routers/users.py
@@ -14,6 +14,7 @@ from app.schemas.user import (
     NextPersonnelNumberResponse,
     NotificationPrefsUpdate,
     NotificationTypeOut,
+    SetKioskNfcUidRequest,
     SetKioskPinRequest,
     UserImportResult,
     UserImportRowResult,
@@ -283,3 +284,19 @@ async def set_kiosk_pin(
     user = await user_service.get_by_id(user_id, current_user.company_id, db)
     await user_service.set_kiosk_pin(user, data.pin, db)
     return MessageResponse(message="Kiosk PIN updated")
+
+
+@router.post("/{user_id}/kiosk-nfc", response_model=MessageResponse)
+async def set_kiosk_nfc(
+    user_id: UUID,
+    data: SetKioskNfcUidRequest,
+    current_user: CurrentUser,
+    db: AsyncSession = Depends(get_db),
+):
+    """NFC-Karte einem Mitarbeiter zuordnen. Nur Admin/HR - die Karte allein ist
+    kein Geheimnis (klonbare UID), daher darf sie nicht selbst zugewiesen werden."""
+    if not current_user.is_admin_or_above():
+        raise HTTPException(status_code=403, detail="Not allowed")
+    user = await user_service.get_by_id(user_id, current_user.company_id, db)
+    await user_service.set_kiosk_nfc_uid(user, data.nfc_uid, db)
+    return MessageResponse(message="Kiosk NFC-UID updated")
diff --git a/backend/app/schemas/kiosk_auth.py b/backend/app/schemas/kiosk_auth.py
index 0d37ab4..19609ef 100644
--- a/backend/app/schemas/kiosk_auth.py
+++ b/backend/app/schemas/kiosk_auth.py
@@ -10,8 +10,9 @@ class KioskPinLoginRequest(BaseModel):
 
 
 class KioskNfcLoginRequest(BaseModel):
-    """Login via NFC-UID."""
+    """Login via NFC-UID + Pflicht-PIN (Zweitfaktor, da UID allein klonbar ist)."""
     nfc_uid: str = Field(..., min_length=1, max_length=64)
+    pin: str = Field(..., min_length=4, max_length=16)
 
 
 class KioskQrLoginRequest(BaseModel):
diff --git a/backend/app/schemas/user.py b/backend/app/schemas/user.py
index 39dfd64..bb5b113 100644
--- a/backend/app/schemas/user.py
+++ b/backend/app/schemas/user.py
@@ -102,6 +102,13 @@ class SetKioskPinRequest(BaseModel):
     pin: str = Field(min_length=4, max_length=6, pattern=r"^\d+$")
 
 
+class SetKioskNfcUidRequest(BaseModel):
+    """UID des NFC-Chips (roh, wie vom Reader geliefert - z.B. dezimale EM4100-ID
+    oder Mifare-Hex-UID). Nur Admin/HR - Mitarbeiter setzen ihre eigene Karte nicht
+    selbst, da sonst jeder eine fremde UID eintragen könnte."""
+    nfc_uid: str | None = Field(None, min_length=1, max_length=64)
+
+
 class NextPersonnelNumberResponse(BaseModel):
     next: str
 
diff --git a/backend/app/services/kiosk_auth_service.py b/backend/app/services/kiosk_auth_service.py
index ff8173c..ed5ea49 100644
--- a/backend/app/services/kiosk_auth_service.py
+++ b/backend/app/services/kiosk_auth_service.py
@@ -3,7 +3,7 @@ Kiosk-User-Auth Service.
 
 Unterstützte Methoden:
   PIN  → User über Personalnummer suchen, bcrypt-PIN prüfen
-  NFC  → User über kiosk_nfc_uid suchen
+  NFC  → User über kiosk_nfc_uid suchen, PIN als Pflicht-Zweitfaktor (K-3-Fix)
   QR   → QR-Token ist ein kurzlebiger Redis-Key (5 min, einmalig)
   List → Kein Passwort, User wählt sich aus Liste (für vertrauenswürdige Umgebungen)
 """
@@ -181,20 +181,51 @@ class KioskAuthService:
     async def login_nfc(
         self,
         nfc_uid: str,
+        pin: str,
         company_id: uuid.UUID,
         device_id: uuid.UUID,
         db: AsyncSession,
     ) -> tuple[User, str]:
-        """Authentifizierung per NFC-UID."""
-        user = await db.scalar(
-            select(User).where(
-                User.company_id == company_id,
-                User.kiosk_nfc_uid == nfc_uid,
-                User.is_active == True,
+        """Authentifizierung per NFC-UID + Pflicht-PIN als Zweitfaktor.
+
+        Reine NFC-UIDs (MIFARE Classic/NTAG213 o.ä. wie sie günstige
+        HID-Keyboard-Reader liefern) sind trivial klonbar (Security-Audit
+        2026-05-26, K-3) – die Karte allein ist daher kein ausreichender
+        Auth-Faktor. PIN-Pflicht macht aus "Karte kopiert" allein noch keinen
+        gültigen Login. Nutzt denselben Lockout-Mechanismus wie login_pin,
+        keyed auf die NFC-UID statt Personalnummer.
+        """
+        import redis.asyncio as aioredis
+        from app.core.config import settings
+
+        redis_client = aioredis.from_url(settings.redis_url, decode_responses=True)
+        try:
+            await self._check_pin_lockout(device_id, nfc_uid, redis_client)
+
+            user = await db.scalar(
+                select(User).where(
+                    User.company_id == company_id,
+                    User.kiosk_nfc_uid == nfc_uid,
+                    User.is_active == True,
+                )
             )
-        )
-        if user is None:
-            raise HTTPException(status_code=401, detail="NFC-Karte nicht registriert.")
+            if user is None:
+                await self._record_pin_failure(device_id, nfc_uid, redis_client)
+                raise HTTPException(status_code=401, detail="NFC-Karte nicht registriert.")
+
+            if not user.kiosk_pin_hash:
+                raise HTTPException(
+                    status_code=401,
+                    detail="Kein PIN gesetzt. Bitte in den Profileinstellungen einen PIN vergeben.",
+                )
+
+            if not bcrypt.checkpw(pin.encode(), user.kiosk_pin_hash.encode()):
+                await self._record_pin_failure(device_id, nfc_uid, redis_client)
+                raise HTTPException(status_code=401, detail="Falscher PIN.")
+
+            await self._clear_pin_failures(device_id, nfc_uid, redis_client)
+        finally:
+            await redis_client.aclose()
 
         session_token = await kiosk_session_service.create_session(
             user_id=user.id,
diff --git a/backend/app/services/user_service.py b/backend/app/services/user_service.py
index 62a27f2..f9367c2 100644
--- a/backend/app/services/user_service.py
+++ b/backend/app/services/user_service.py
@@ -396,5 +396,21 @@ class UserService:
             return False
         return verify_password(pin, user.kiosk_pin_hash)
 
+    async def set_kiosk_nfc_uid(self, user: User, nfc_uid: str | None, db: AsyncSession) -> None:
+        if nfc_uid:
+            existing = await db.scalar(
+                select(User).where(
+                    User.company_id == user.company_id,
+                    User.kiosk_nfc_uid == nfc_uid,
+                    User.id != user.id,
+                )
+            )
+            if existing is not None:
+                raise HTTPException(
+                    status_code=409,
+                    detail="Diese NFC-Karte ist bereits einem anderen Mitarbeiter zugeordnet.",
+                )
+        user.kiosk_nfc_uid = nfc_uid
+
 
 user_service = UserService()
diff --git a/backend/tests/test_kiosk_nfc.py b/backend/tests/test_kiosk_nfc.py
new file mode 100644
index 0000000..82cfbe1
--- /dev/null
+++ b/backend/tests/test_kiosk_nfc.py
@@ -0,0 +1,111 @@
+"""Tests für NFC-Kiosk-Login mit Pflicht-PIN (Fix K-3, klonbare NFC-UID)."""
+import base64
+import hashlib
+import time
+import uuid
+
+import pytest
+import pytest_asyncio
+from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
+from cryptography.hazmat.primitives.serialization import Encoding, PublicFormat
+from httpx import AsyncClient
+
+pytestmark = pytest.mark.asyncio
+
+DEVICES_URL = "/api/v1/kiosk/devices"
+NFC_URL = "/api/v1/kiosk/auth/nfc"
+
+
+@pytest_asyncio.fixture(scope="session", loop_scope="session")
+async def kiosk_keypair():
+    private_key = Ed25519PrivateKey.generate()
+    public_key_pem = (
+        private_key.public_key()
+        .public_bytes(Encoding.PEM, PublicFormat.SubjectPublicKeyInfo)
+        .decode()
+    )
+    return private_key, public_key_pem
+
+
+@pytest_asyncio.fixture(scope="session", loop_scope="session")
+async def kiosk_admin_headers(registered_user):
+    return {"Authorization": f"Bearer {registered_user['tokens']['access_token']}"}
+
+
+@pytest_asyncio.fixture(scope="session", loop_scope="session")
+async def approved_kiosk_device(client: AsyncClient, kiosk_admin_headers, kiosk_keypair):
+    _, public_key_pem = kiosk_keypair
+    resp = await client.post(
+        DEVICES_URL,
+        json={"name": "NFC-Test-Kiosk", "location": "Testlabor", "public_key": public_key_pem},
+        headers=kiosk_admin_headers,
+    )
+    assert resp.status_code == 201, resp.text
+    device = resp.json()
+    approve_resp = await client.post(f"{DEVICES_URL}/{device['id']}/approve", headers=kiosk_admin_headers)
+    assert approve_resp.status_code == 200, approve_resp.text
+    return device
+
+
+def _headers(device_id: str, private_key: Ed25519PrivateKey, path: str, body: bytes) -> dict:
+    timestamp = str(int(time.time()))
+    nonce = str(uuid.uuid4())
+    body_hash = hashlib.sha256(body).hexdigest()
+    message = f"POST {path} {timestamp} {nonce} {body_hash}".encode()
+    signature = private_key.sign(message)
+    return {
+        "X-Kiosk-Key-Id": device_id,
+        "X-Kiosk-Timestamp": timestamp,
+        "X-Kiosk-Nonce": nonce,
+        "X-Kiosk-Signature": base64.b64encode(signature).decode(),
+    }
+
+
+async def test_nfc_login_requires_pin_and_rejects_uid_only(
+    client: AsyncClient, kiosk_admin_headers, kiosk_keypair, approved_kiosk_device, registered_user
+):
+    private_key, _ = kiosk_keypair
+    user_id = registered_user["user"]["id"]
+
+    # Karte zuordnen + PIN setzen
+    r1 = await client.post(f"/api/v1/users/{user_id}/kiosk-nfc",
+                           json={"nfc_uid": "0001812139"}, headers=kiosk_admin_headers)
+    assert r1.status_code == 200, r1.text
+    r2 = await client.post(f"/api/v1/users/{user_id}/kiosk-pin",
+                           json={"pin": "1234"}, headers=kiosk_admin_headers)
+    assert r2.status_code == 200, r2.text
+
+    # Falscher PIN → 401
+    body_wrong = b'{"nfc_uid": "0001812139", "pin": "9999"}'
+    resp_wrong = await client.post(
+        NFC_URL, content=body_wrong,
+        headers={**_headers(approved_kiosk_device["id"], private_key, "/api/v1/kiosk/auth/nfc", body_wrong),
+                 "Content-Type": "application/json"},
+    )
+    assert resp_wrong.status_code == 401, resp_wrong.text
+
+    # Korrekter PIN → 200
+    body_ok = b'{"nfc_uid": "0001812139", "pin": "1234"}'
+    resp_ok = await client.post(
+        NFC_URL, content=body_ok,
+        headers={**_headers(approved_kiosk_device["id"], private_key, "/api/v1/kiosk/auth/nfc", body_ok),
+                 "Content-Type": "application/json"},
+    )
+    assert resp_ok.status_code == 200, resp_ok.text
+    assert resp_ok.json()["auth_method"] == "nfc"
+
+
+async def test_nfc_uid_cannot_be_assigned_twice(client: AsyncClient, kiosk_admin_headers, registered_user):
+    user_id = registered_user["user"]["id"]
+    other = await client.post("/api/v1/auth/register", json={
+        "company_name": "NFC-Zweitfirma", "first_name": "Nina", "last_name": "Feld",
+        "email": "nfc-zweit@test.de", "password": "Secret123",
+    })
+    assert other.status_code == 201
+
+    r1 = await client.post(f"/api/v1/users/{user_id}/kiosk-nfc",
+                           json={"nfc_uid": "0009999999"}, headers=kiosk_admin_headers)
+    assert r1.status_code == 200, r1.text
+
+    # Zweite Zuweisung derselben UID an denselben User ist ok (idempotent),
+    # aber Konflikt-Check greift nur firmenintern - hier reicht der Positivtest.