diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index 9c9d083b..314f7547 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -65,3 +65,7 @@
 **Vulnerability:** Path traversal in `media_shrinker.py` via unresolved `..` segments or symlink escapes before deriving conversion output paths.
 **Learning:** `Path.relative_to()` is only a lexical containment check unless both the source and root have first been resolved into canonical absolute paths. Relative paths and symlinks can otherwise bypass root-boundary assumptions.
 **Prevention:** Resolve both source and root once, reject sources outside the resolved root with a sanitized `MediaShrinkerError`, and derive `rel_source` from the resolved paths before planning outputs.
+## 2024-08-16 - hmac.compare_digest의 유니코드 문자열 처리 취약점
+**취약점:** `hmac.compare_digest`에 비ASCII 문자열(예: 이모지)을 포함한 값을 전달할 경우 `TypeError`가 발생하여 500 Server Error DoS 공격을 유발할 수 있음.
+**학습:** 파이썬의 `hmac.compare_digest`는 비ASCII 문자를 포함한 문자열 비교를 지원하지 않아 예외를 발생시킨다. 악의적인 사용자가 이를 이용해 잘못된 헤더 값을 전송하여 서버를 강제로 종료시키거나 장애를 유발할 수 있다.
+**예방:** `hmac.compare_digest`를 호출하기 전에 항상 두 인자를 명시적으로 바이트(`.encode('utf-8')`)로 인코딩하여 비교해야 한다.
diff --git a/saas_web.py b/saas_web.py
index 63265e94..071b1419 100644
--- a/saas_web.py
+++ b/saas_web.py
@@ -114,7 +114,7 @@ async def require_api_key(request: Request, call_next):
     if configured_keys and not (request.method == "GET" and request.url.path == "/"):
         provided_key = request.headers.get("x-api-key", "")
         if not any(
-            hmac.compare_digest(provided_key, key) for key in configured_keys
+            hmac.compare_digest(provided_key.encode("utf-8"), key.encode("utf-8")) for key in configured_keys
         ):
             return JSONResponse(
                 status_code=401,
diff --git a/tests/test_saas_web.py b/tests/test_saas_web.py
index 3b57e033..eb706b0f 100644
--- a/tests/test_saas_web.py
+++ b/tests/test_saas_web.py
@@ -1222,6 +1222,25 @@ def test_video_content_type_accepted_by_validator(self):
             )
         )
 
+    @patch.dict(os.environ, {"CODEC_CARVER_API_KEYS": "test-key"})
+    def test_unicode_api_key_dos(self):
+        from starlette.requests import Request
+        import asyncio
+        async def mock_call_next(request):
+            return "SUCCESS"
+        scope = {
+            'type': 'http',
+            'method': 'POST',
+            'path': '/shrink',
+            'headers': [(b'x-api-key', 'test-key😀'.encode('utf-8'))],
+        }
+        req = Request(scope)
+        try:
+            res = asyncio.run(saas_web.require_api_key(req, mock_call_next))
+            self.assertEqual(res.status_code, 401)
+        except Exception as e:
+            self.fail(f"Middleware crashed with exception: {e}")
+
 
 if __name__ == "__main__":
     unittest.main()