diff -r 80c7d63325f6 Lib/http/cookies.py
--- a/Lib/http/cookies.py	Wed Jun 29 13:44:05 2011 +0200
+++ b/Lib/http/cookies.py	Wed Jun 29 15:27:30 2011 +0100
@@ -552,8 +552,13 @@
                     M[key] = _unquote(value)
             else:
                 rval, cval = self.value_decode(value)
-                self.__set(key, rval, cval)
-                M = self[key]
+                try:
+                    self.__set(key, rval, cval)
+                    M = self[key]
+                except CookieError:
+                    # Postel's law - ignore error.
+                    # Any attributes for an invalid name should also be dropped.
+                    M = None
 
 
 class SimpleCookie(BaseCookie):
diff -r 80c7d63325f6 Lib/test/test_http_cookies.py
--- a/Lib/test/test_http_cookies.py	Wed Jun 29 13:44:05 2011 +0200
+++ b/Lib/test/test_http_cookies.py	Wed Jun 29 15:27:30 2011 +0100
@@ -77,6 +77,21 @@
         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 = cookies.SimpleCookie()
+        self.assertRaises(cookies.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_special_attrs(self):
         # 'expires'
         C = cookies.SimpleCookie('Customer="WILE_E_COYOTE"')