diff -r 25683ceaf341 Lib/httplib.py
--- a/Lib/httplib.py	Tue Sep 03 14:47:00 2013 +0200
+++ b/Lib/httplib.py	Wed Sep 04 11:59:52 2013 +0200
@@ -211,6 +211,10 @@
 # maximal amount of data to read at one time in _safe_read
 MAXAMOUNT = 1048576
 
+# maximum amount of headers accepted
+_MAXHEADERS = 100
+
+
 class HTTPMessage(mimetools.Message):
 
     def addheader(self, key, value):
@@ -267,6 +271,8 @@
         elif self.seekable:
             tell = self.fp.tell
         while True:
+            if len(hlist) > _MAXHEADERS:
+                raise TooManyHeaders()
             if tell:
                 try:
                     startofline = tell()
@@ -1203,6 +1209,11 @@
         self.args = line,
         self.line = line
 
+
+class TooManyHeaders(HTTPException):
+    def __init__(self):
+        HTTPException.__init__(self, "got more than %d headers" % _MAXHEADERS)
+
 # for backwards compatibility
 error = HTTPException
 
diff -r 25683ceaf341 Lib/test/test_httplib.py
--- a/Lib/test/test_httplib.py	Tue Sep 03 14:47:00 2013 +0200
+++ b/Lib/test/test_httplib.py	Wed Sep 04 11:59:52 2013 +0200
@@ -152,6 +152,13 @@
         if resp.read() != "":
             self.fail("Did not expect response from HEAD request")
 
+    def test_too_many_headers(self):
+        headers = '\r\n'.join('Header%d: foo' % i for i in xrange(200)) + '\r\n'
+        text = ('HTTP/1.1 200 OK\r\n' + headers)
+        s = FakeSocket(text)
+        r = httplib.HTTPResponse(s)
+        self.assertRaises(httplib.TooManyHeaders, r.begin)
+
     def test_send_file(self):
         expected = 'GET /foo HTTP/1.1\r\nHost: example.com\r\n' \
                    'Accept-Encoding: identity\r\nContent-Length:'