diff -r 178f9042af81 Lib/http/server.py
--- a/Lib/http/server.py	Sun Sep 23 11:11:07 2012 +0200
+++ b/Lib/http/server.py	Fri Sep 28 17:16:04 2012 +0200
@@ -691,8 +691,13 @@
 
         """
         path = self.translate_path(self.path)
-        f = None
-        if os.path.isdir(path):
+        try:
+            isdir = os.path.isdir(path)
+        except TypeError:
+            # client sent invalid bytes, see issue #16083
+            self.send_error(400)
+            return
+        if isdir:
             if not self.path.endswith('/'):
                 # redirect browser - doing basically what apache does
                 self.send_response(301)
diff -r 178f9042af81 Lib/test/test_httpservers.py
--- a/Lib/test/test_httpservers.py	Sun Sep 23 11:11:07 2012 +0200
+++ b/Lib/test/test_httpservers.py	Fri Sep 28 17:16:04 2012 +0200
@@ -284,6 +284,9 @@
         self.check_status_and_reason(response, 501)
         response = self.request('/', method='GETs')
         self.check_status_and_reason(response, 501)
+        # send NUL byte. See issue16083
+        response = self.request('/\00', method='GET')
+        self.check_status_and_reason(response, 400)
 
 
 cgi_file1 = """\