diff -r 68d1ac152b5d Lib/http/server.py
--- a/Lib/http/server.py	Mon Apr 29 10:23:08 2013 -0400
+++ b/Lib/http/server.py	Wed May 01 23:47:56 2013 +0300
@@ -126,6 +126,11 @@
 def _quote_html(html):
     return html.replace("&", "&amp;").replace("<", "&lt;").replace(">", "&gt;")
 
+# http://tools.ietf.org/html/rfc2616#section-6.1.1
+def _is_valid_status_code(code):
+        return isinstance(code, int) and 0 <= code <= 999
+
+
 class HTTPServer(socketserver.TCPServer):
 
     allow_reuse_address = 1    # Seems to make sense in testing environment
@@ -413,7 +418,7 @@
         a piece of HTML explaining the error to the user.
 
         """
-
+        code = _is_valid_status_code(code) and code or 500
         try:
             shortmsg, longmsg = self.responses[code]
         except KeyError:
@@ -440,6 +445,7 @@
         version and the current date.
 
         """
+        code = _is_valid_status_code(code) and code or 500
         self.log_request(code)
         self.send_response_only(code, message)
         self.send_header('Server', self.version_string())
diff -r 68d1ac152b5d Lib/test/test_httpservers.py
--- a/Lib/test/test_httpservers.py	Mon Apr 29 10:23:08 2013 -0400
+++ b/Lib/test/test_httpservers.py	Wed May 01 23:47:56 2013 +0300
@@ -98,6 +98,12 @@
             self.send_header('Connection', 'close')
             self.end_headers()
 
+        def do_INCORRECT(self):
+            self.send_response('incorrect_status')
+            self.send_header('Content-Type', 'text/html')
+            self.send_header('Connection', 'close')
+            self.end_headers()
+
         def do_LATINONEHEADER(self):
             self.send_response(999)
             self.send_header('X-Special', 'Dängerous Mind')
@@ -203,6 +209,11 @@
         res = self.con.getresponse()
         self.assertEqual(res.status, 999)
 
+    def test_trying_to_return_incorrect_status(self):
+        self.con.request('INCORRECT', '/')
+        res = self.con.getresponse()
+        self.assertEqual(res.status, 500)
+
     def test_latin1_header(self):
         self.con.request('LATINONEHEADER', '/', headers={
             'X-Special-Incoming':       'Ärger mit Unicode'