diff --git a/gateway/platforms/bluebubbles.py b/gateway/platforms/bluebubbles.py
index 31595b223b54..62affe7c3c82 100644
--- a/gateway/platforms/bluebubbles.py
+++ b/gateway/platforms/bluebubbles.py
@@ -9,6 +9,7 @@
 """
 
 import asyncio
+import hmac
 import json
 import logging
 import os
@@ -864,6 +865,12 @@ def _value(*candidates: Any) -> Optional[str]:
     async def _handle_webhook(self, request):
         from aiohttp import web
 
+        # Fail closed: an unconfigured password must reject every request
+        # rather than authenticating callers who omit the token (``token`` is
+        # None/"" in that case, which would otherwise compare equal to an
+        # empty ``self.password``).
+        if not self.password:
+            return web.json_response({"error": "unauthorized"}, status=401)
         token = (
             request.query.get("password")
             or request.query.get("guid")
@@ -871,7 +878,14 @@ async def _handle_webhook(self, request):
             or request.headers.get("x-guid")
             or request.headers.get("x-bluebubbles-guid")
         )
-        if token != self.password:
+        # Constant-time comparison so a mismatch can't be recovered from
+        # response-timing side channels. Compare UTF-8 bytes: ``hmac.compare_digest``
+        # on str raises TypeError for non-ASCII code points, which would turn
+        # hostile/Unicode credentials into HTTP 500 instead of 401 and break
+        # legitimately configured non-ASCII passwords.
+        token_b = str(token or "").encode("utf-8")
+        password_b = str(self.password).encode("utf-8")
+        if not hmac.compare_digest(token_b, password_b):
             return web.json_response({"error": "unauthorized"}, status=401)
         try:
             raw = await request.read()
diff --git a/tests/gateway/test_bluebubbles.py b/tests/gateway/test_bluebubbles.py
index 7d4a71378c0b..c0b681914ae7 100644
--- a/tests/gateway/test_bluebubbles.py
+++ b/tests/gateway/test_bluebubbles.py
@@ -174,6 +174,100 @@ async def read(self):
         return self._body
 
 
+class TestBlueBubblesWebhookAuth:
+    @pytest.mark.asyncio
+    async def test_webhook_rejects_wrong_password(self, monkeypatch):
+        adapter = _make_adapter(monkeypatch)
+        handled = []
+
+        async def fake_handle_message(event):
+            handled.append(event)
+
+        monkeypatch.setattr(adapter, "handle_message", fake_handle_message)
+        response = await adapter._handle_webhook(
+            _FakeBlueBubblesRequest({"type": "new-message"}, password="wrong")
+        )
+        await asyncio.sleep(0)
+
+        assert response.status == 401
+        assert handled == []
+
+    @pytest.mark.asyncio
+    async def test_webhook_rejects_wrong_unicode_password(self, monkeypatch):
+        adapter = _make_adapter(monkeypatch, password="s3cret")
+        handled = []
+
+        async def fake_handle_message(event):
+            handled.append(event)
+
+        monkeypatch.setattr(adapter, "handle_message", fake_handle_message)
+        response = await adapter._handle_webhook(
+            _FakeBlueBubblesRequest({"type": "new-message"}, password="пароль-неверный")
+        )
+        await asyncio.sleep(0)
+
+        assert response.status == 401
+        assert handled == []
+
+    @pytest.mark.asyncio
+    async def test_webhook_accepts_configured_unicode_password(self, monkeypatch):
+        unicode_pw = "pässwörd-密钥"
+        adapter = _make_adapter(monkeypatch, password=unicode_pw)
+        handled = []
+
+        async def fake_handle_message(event):
+            handled.append(event)
+
+        monkeypatch.setattr(adapter, "handle_message", fake_handle_message)
+        response = await adapter._handle_webhook(
+            _FakeBlueBubblesRequest(
+                {
+                    "type": "new-message",
+                    "data": {
+                        "guid": "msg-unicode-auth",
+                        "text": "hello",
+                        "handle": {"address": "+15555550100"},
+                        "isFromMe": False,
+                        "isGroup": False,
+                        "chats": [{"guid": "iMessage;-;+15555550100"}],
+                    },
+                },
+                password=unicode_pw,
+            )
+        )
+        await asyncio.sleep(0)
+
+        assert response.status == 200
+        assert len(handled) == 1
+
+    @pytest.mark.asyncio
+    async def test_connect_fails_closed_when_password_unconfigured(self, monkeypatch):
+        # Lifecycle invariant: connect() returns early when password is falsy
+        # (gateway/platforms/bluebubbles.py), so an unconfigured adapter never
+        # binds the aiohttp webhook route. Do not mutate adapter.password after
+        # construction to simulate that state — assert connect() itself refuses.
+        monkeypatch.setenv("BLUEBUBBLES_SERVER_URL", "http://localhost:1234")
+        monkeypatch.delenv("BLUEBUBBLES_PASSWORD", raising=False)
+        from gateway.config import PlatformConfig
+        from gateway.platforms.bluebubbles import BlueBubblesAdapter
+
+        cfg = PlatformConfig(
+            enabled=True,
+            extra={
+                "server_url": "http://localhost:1234",
+                # explicit empty password: unconfigured webhook auth
+                "password": "",
+            },
+        )
+        adapter = BlueBubblesAdapter(cfg)
+        assert not adapter.password
+        ok = await adapter.connect()
+        assert ok is False
+        # No webhook app should have been started for an unconfigured adapter.
+        assert getattr(adapter, "_runner", None) is None
+        assert getattr(adapter, "_site", None) is None
+
+
 class TestBlueBubblesMentionGating:
     @pytest.mark.asyncio
     async def test_group_message_without_mention_is_acknowledged_and_skipped(self, monkeypatch):