diff -r 831be7dc260a Doc/library/http.cookies.rst
--- a/Doc/library/http.cookies.rst	Sat Feb 23 07:53:56 2013 +0200
+++ b/Doc/library/http.cookies.rst	Sat Feb 23 17:30:50 2013 +0100
@@ -106,7 +106,8 @@
 .. method:: BaseCookie.load(rawdata)
 
    If *rawdata* is a string, parse it as an ``HTTP_COOKIE`` and add the values
-   found there as :class:`Morsel`\ s. If it is a dictionary, it is equivalent to::
+   found there as :class:`Morsel`\ s. In case the string contains duplicate
+   keys, the first value is used.  If it is a dictionary, it is equivalent to::
 
       for k, v in rawdata.items():
           cookie[k] = v
diff -r 831be7dc260a Lib/http/cookies.py
--- a/Lib/http/cookies.py	Sat Feb 23 07:53:56 2013 +0200
+++ b/Lib/http/cookies.py	Sat Feb 23 17:30:50 2013 +0100
@@ -529,6 +529,7 @@
         i = 0            # Our starting point
         n = len(str)     # Length of string
         M = None         # current morsel
+        keys = set()     # Keys found in string
 
         while 0 <= i < n:
             # Start looking for a cookie
@@ -540,6 +541,13 @@
             key, value = match.group("key"), match.group("val")
             i = match.end(0)
 
+            # If a key is duplicated in the string,
+            # only use the first value and ignore duplicates
+            if key in keys:
+                continue
+            else:
+                keys.add(key)
+
             # Parse the key, value in case it's metainfo
             if key[0] == "$":
                 # We ignore attributes which pertain to the cookie
diff -r 831be7dc260a Lib/test/test_http_cookies.py
--- a/Lib/test/test_http_cookies.py	Sat Feb 23 07:53:56 2013 +0200
+++ b/Lib/test/test_http_cookies.py	Sat Feb 23 17:30:50 2013 +0100
@@ -29,6 +29,12 @@
              'repr': '''<SimpleCookie: keebler='E=mc2; L="Loves"; fudge=\\n;'>''',
              'output': 'Set-Cookie: keebler="E=mc2; L=\\"Loves\\"; fudge=\\012;"'},
 
+            # Check that first value for a duplicate key is used
+            {'data': 'duplicate=first; duplicate=second',
+             'dict': {'duplicate':'first'},
+             'repr': "<SimpleCookie: duplicate='first'>",
+             'output': 'Set-Cookie: duplicate=first'},
+
             # Check illegal cookies that have an '=' char in an unquoted value
             {'data': 'keebler=E=mc2',
              'dict': {'keebler' : 'E=mc2'},