diff -r cdfcd00873cd Lib/Cookie.py
--- a/Lib/Cookie.py	Tue Jun 28 20:13:03 2011 -0700
+++ b/Lib/Cookie.py	Wed Jun 29 15:29:20 2011 +0100
@@ -662,8 +662,13 @@
                     M[ K ] = _unquote(V)
             else:
                 rval, cval = self.value_decode(V)
-                self.__set(K, rval, cval)
-                M = self[K]
+                try:
+                    self.__set(K, rval, cval)
+                    M = self[K]
+                except CookieError:
+                    # Postel's law - ignore error.
+                    # Any attributes for an invalid name should also be dropped.
+                    M = None
     # end __ParseString
 # end BaseCookie class
 
diff -r cdfcd00873cd Lib/test/test_cookie.py
--- a/Lib/test/test_cookie.py	Tue Jun 28 20:13:03 2011 -0700
+++ b/Lib/test/test_cookie.py	Wed Jun 29 15:29:20 2011 +0100
@@ -80,6 +80,21 @@
         self.assertEqual(C.output(['val']),
             'Set-Cookie: val="some\\054funky\\073stuff"')
 
+    def test_illegal_names(self):
+        # Issue 2193: various servers/browsers use/support cookies with ':' in
+        # the name (RFC2109 notwithstanding). We should deal with them
+        # gracefully. This means we silently ignore when loading, but raise
+        # exception when setting in other situations.
+
+        C = Cookie.SimpleCookie()
+        self.assertRaises(Cookie.CookieError,
+                              C.__setitem__, 'invalid:name', 'a value')
+
+        C.load('validname=value; invalid:name=value; expires=Wed, 01-Jan-2010 00:00:00 GMT;')
+        self.assertEqual(repr(C), "<SimpleCookie: validname='value'>")
+        # Ensure the 'expires' is not attached to 'validname'
+        self.assertEqual(C.output(), "Set-Cookie: validname=value")
+
     def test_quoted_meta(self):
         # Try cookie with quoted meta-data
         C = Cookie.SimpleCookie()