diff --git i/Lib/http/client.py w/Lib/http/client.py
index 5466d06..bac1eb6 100644
--- i/Lib/http/client.py
+++ w/Lib/http/client.py
@@ -206,6 +206,8 @@ MAXAMOUNT = 1048576
 
 # maximal line length when calling readline().
 _MAXLINE = 65536
+_MAXHEADERS = 100
+
 
 class HTTPMessage(email.message.Message):
     # XXX The only usage of this method is in
@@ -253,6 +255,8 @@ def parse_headers(fp, _class=HTTPMessage):
         if len(line) > _MAXLINE:
             raise LineTooLong("header line")
         headers.append(line)
+        if len(headers) > _MAXHEADERS:
+            raise TooMuchHeaders()
         if line in (b'\r\n', b'\n', b''):
             break
     hstring = b''.join(headers).decode('iso-8859-1')
@@ -1192,5 +1196,10 @@ class LineTooLong(HTTPException):
         HTTPException.__init__(self, "got more than %d bytes when reading %s"
                                      % (_MAXLINE, line_type))
 
+
+class TooMuchHeaders(HTTPException):
+    def __init__(self):
+        HTTPException.__init__(self, "got more than %d headers" % _MAXHEADERS)
+
 # for backwards compatibility
 error = HTTPException
diff --git i/Lib/test/test_httplib.py w/Lib/test/test_httplib.py
index 420302c..99370fb 100644
--- i/Lib/test/test_httplib.py
+++ w/Lib/test/test_httplib.py
@@ -272,6 +272,13 @@ class BasicTest(TestCase):
         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 range(200)) + '\r\n'
+        text = ('HTTP/1.1 200 OK\r\n' + headers)
+        s = FakeSocket(text)
+        r = client.HTTPResponse(s)
+        self.assertRaises(client.TooMuchHeaders, r.begin)
+
     def test_send_file(self):
         expected = (b'GET /foo HTTP/1.1\r\nHost: example.com\r\n'
                     b'Accept-Encoding: identity\r\nContent-Length:')