diff -r 0e7c4203bd79 Lib/httplib.py
--- a/Lib/httplib.py	Wed Dec 18 11:25:26 2013 -0800
+++ b/Lib/httplib.py	Wed Dec 18 21:13:22 2013 +0000
@@ -307,6 +307,11 @@
                 hlist.append(line)
                 self.addheader(headerseen, line[len(headerseen)+1:].strip())
                 continue
+            elif headerseen is not None:
+                # An empty header name. These aren't allowed in HTTP, but it's
+                # probably a benign mistake. Don't add the header, just keep
+                # going.
+                continue
             else:
                 # It's not a header line; throw it back and stop here.
                 if not self.dict:
diff -r 0e7c4203bd79 Lib/rfc822.py
--- a/Lib/rfc822.py	Wed Dec 18 11:25:26 2013 -0800
+++ b/Lib/rfc822.py	Wed Dec 18 21:13:22 2013 +0000
@@ -179,6 +179,11 @@
                 lst.append(line)
                 self.dict[headerseen] = line[len(headerseen)+1:].strip()
                 continue
+            elif headerseen is not None:
+                # An empty header name. These aren't allowed in HTTP, but it's
+                # probably a benign mistake. Don't add the header, just keep
+                # going.
+                continue
             else:
                 # It's not a header line; throw it back and stop here.
                 if not self.dict:
@@ -202,7 +207,7 @@
         data in RFC 2822-like formats with special header formats.
         """
         i = line.find(':')
-        if i > 0:
+        if i > -1:
             return line[:i].lower()
         return None
 
diff -r 0e7c4203bd79 Lib/test/test_httplib.py
--- a/Lib/test/test_httplib.py	Wed Dec 18 11:25:26 2013 -0800
+++ b/Lib/test/test_httplib.py	Wed Dec 18 21:13:22 2013 +0000
@@ -144,6 +144,17 @@
         conn.request('GET', '/foo')
         self.assertTrue(sock.data.startswith(expected))
 
+    def test_malformed_headers_coped_with(self):
+        # Issue 19996
+        body = "HTTP/1.1 200 OK\r\nFirst: val\r\n: nval\r\nSecond: val\r\n\r\n"
+        sock = FakeSocket(body)
+        resp = httplib.HTTPResponse(sock)
+        resp.begin()
+
+        self.assertEqual(resp.getheader('First'), 'val')
+        self.assertEqual(resp.getheader('Second'), 'val')
+
+
 
 class BasicTest(TestCase):
     def test_status_lines(self):
diff -r 0e7c4203bd79 Lib/test/test_rfc822.py
--- a/Lib/test/test_rfc822.py	Wed Dec 18 11:25:26 2013 -0800
+++ b/Lib/test/test_rfc822.py	Wed Dec 18 21:13:22 2013 +0000
@@ -248,6 +248,12 @@
         eq(rfc822.quote('foo\\wacky"name'), 'foo\\\\wacky\\"name')
         eq(rfc822.unquote('"foo\\\\wacky\\"name"'), 'foo\\wacky"name')
 
+    def test_invalid_headers(self):
+        eq = self.assertEqual
+        msg = self.create_message("First: val\n: otherval\nSecond: val2\n")
+        eq(msg.getheader('First'), 'val')
+        eq(msg.getheader('Second'), 'val2')
+
 
 def test_main():
     test_support.run_unittest(MessageTestCase)