diff --git a/app/core/config.py b/app/core/config.py
index f4bede6..f0e49fd 100644
--- a/app/core/config.py
+++ b/app/core/config.py
@@ -42,9 +42,10 @@ class Settings(BaseSettings):
     @computed_field  # type: ignore[prop-decorator]
     @property
     def all_cors_origins(self) -> list[str]:
-        return [str(origin).rstrip("/") for origin in self.BACKEND_CORS_ORIGINS] + [
-            self.FRONTEND_HOST
-        ]
+        origins = [str(origin).rstrip("/") for origin in self.BACKEND_CORS_ORIGINS]
+        if self.FRONTEND_HOST:
+            origins.append(str(self.FRONTEND_HOST).rstrip("/"))
+        return origins
 
     PROJECT_NAME: str
     SENTRY_DSN: str | None = None
diff --git a/app/main.py b/app/main.py
index 2b78964..7f943cf 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1,6 +1,7 @@
 import sentry_sdk
-from fastapi import FastAPI
+from fastapi import FastAPI, Request
 from fastapi.exceptions import RequestValidationError
+from fastapi.responses import JSONResponse
 from fastapi.routing import APIRoute
 from slowapi.errors import RateLimitExceeded
 from starlette.exceptions import HTTPException
@@ -14,6 +15,7 @@
 )
 from app.api.main import api_router
 from app.core.config import settings
+from app.core.messages.error_message import ErrorMessages
 from app.core.rate_limit import limiter
 
 
@@ -38,6 +40,40 @@ def custom_generate_unique_id(route: APIRoute) -> str:
 app.add_exception_handler(RateLimitExceeded, rate_limit_exception_handler)
 app.state.limiter = limiter
 
+
+@app.middleware("http")
+async def origin_check_middleware(request: Request, call_next):
+    """
+    Strict origin check. Returns 404 for unauthorized origins.
+    Allows same-origin requests (from the API's own origin).
+    Hides error details and ensures always 404 for these cases.
+    """
+    origin = request.headers.get("origin")
+    if origin:
+        origin = origin.rstrip("/")
+
+    # Allow same-origin requests
+    if origin:
+        # Reconstruct the request's own origin from scheme and host header
+        scheme = request.url.scheme
+        host = request.headers.get("host", "").rstrip("/")
+        request_origin = f"{scheme}://{host}".rstrip("/")
+
+        # Allow if origins match (same-origin request)
+        if origin == request_origin:
+            return await call_next(request)
+
+    allowed_origins = settings.all_cors_origins
+
+    if origin and allowed_origins and "*" not in allowed_origins:
+        if origin not in allowed_origins:
+            return JSONResponse(
+                status_code=404,
+                content={"success": False, "error": ErrorMessages.RESOURCE_NOT_FOUND},
+            )
+    return await call_next(request)
+
+
 # Set all CORS enabled origins
 if settings.all_cors_origins:
     app.add_middleware(
diff --git a/app/tests/test_origin_restriction.py b/app/tests/test_origin_restriction.py
new file mode 100644
index 0000000..45a1c1f
--- /dev/null
+++ b/app/tests/test_origin_restriction.py
@@ -0,0 +1,81 @@
+import pytest
+from httpx import AsyncClient
+
+from app.core.config import settings
+
+
+@pytest.mark.asyncio
+async def test_allowed_origin(client: AsyncClient):
+    # Use an origin from settings.all_cors_origins
+    # settings.all_cors_origins includes FRONTEND_HOST
+    allowed_origin = settings.FRONTEND_HOST
+    response = await client.get(
+        "/users/me",  # Correct path
+        headers={"Origin": allowed_origin},
+    )
+    # It should not be 404 due to origin (might be 401 if not logged in, but not 404)
+    assert response.status_code != 404
+
+
+@pytest.mark.asyncio
+async def test_unauthorized_origin(client: AsyncClient):
+    response = await client.get(
+        "/auth/login",  # Use an endpoint that exists
+        headers={"Origin": "http://malicious.com"},
+    )
+    assert response.status_code == 404
+    assert response.json() == {"success": False, "error": "RESOURCE_NOT_FOUND"}
+
+
+@pytest.mark.asyncio
+async def test_no_origin(client: AsyncClient):
+    response = await client.get("/auth/login")
+    # Should not be 404 due to missing origin
+    assert response.status_code != 404
+    # If /health doesn't exist, this might fail, but let's check a known endpoint
+    pass
+
+
+@pytest.mark.asyncio
+async def test_same_origin_post(client: AsyncClient):
+    """Test that same-origin POST requests are allowed (not blocked with 404)."""
+    # The client fixture uses http://test as the base origin (from conftest base_url)
+    same_origin = "http://test"
+
+    response = await client.post(
+        "/auth/logout",  # Correct path (base_url already includes /api/v1)
+        headers={"Origin": same_origin},
+    )
+
+    # Should NOT be 404 due to origin check (may fail with 401 if not authenticated, but not 404)
+    assert response.status_code != 404, (
+        "Same-origin POST request should not be blocked with 404"
+    )
+
+
+@pytest.mark.asyncio
+async def test_same_origin_put(client: AsyncClient):
+    """Test that same-origin PUT requests are allowed (not blocked with 404)."""
+    same_origin = "http://test"
+
+    response = await client.put(
+        "/users/me",
+        headers={"Origin": same_origin},
+    )
+
+    # Should NOT be 404 due to origin check (may fail with 401/422, but not 404)
+    assert response.status_code != 404, (
+        "Same-origin PUT request should not be blocked with 404"
+    )
+
+
+@pytest.mark.asyncio
+async def test_cross_origin_post_blocked(client: AsyncClient):
+    """Test that cross-origin POST requests are still blocked (404)."""
+    response = await client.post(
+        "/auth/logout",
+        headers={"Origin": "http://malicious.com"},
+    )
+
+    assert response.status_code == 404
+    assert response.json() == {"success": False, "error": "RESOURCE_NOT_FOUND"}