diff -r 24dfe7310cc1 Lib/http/client.py
--- a/Lib/http/client.py	Sun Nov 23 17:06:39 2014 -0600
+++ b/Lib/http/client.py	Mon Nov 24 03:22:01 2014 +0100
@@ -1124,12 +1124,16 @@
 
         if hasattr(header, 'encode'):
             header = header.encode('ascii')
+        if b'\n' in header or b'\r' in header:
+            raise CannotSendHeader()
         values = list(values)
         for i, one_value in enumerate(values):
             if hasattr(one_value, 'encode'):
                 values[i] = one_value.encode('latin-1')
             elif isinstance(one_value, int):
                 values[i] = str(one_value).encode('ascii')
+            if b'\n' in values[i] or b'\r' in values[i]:
+                raise CannotSendHeader()
         value = b'\r\n\t'.join(values)
         header = header + b': ' + value
         self._output(header)