diff -r 089146b8ccc6 Lib/http/server.py
--- a/Lib/http/server.py	Fri Sep 25 00:49:44 2015 -0400
+++ b/Lib/http/server.py	Sat Sep 26 11:46:52 2015 +0800
@@ -844,6 +844,10 @@
     Raises: IndexError if too many '..' occur within the path.
 
     """
+    # Query component should not be involved.
+    path, _, query = path.partition('?')
+    path = urllib.parse.unquote(path)
+
     # Similar to os.path.split(os.path.normpath(path)) but specific to URL
     # path semantics rather than local operating system semantics.
     path_parts = path.split('/')
@@ -864,6 +868,9 @@
     else:
         tail_part = ''
 
+    if query:
+        tail_part = '?'.join((tail_part, query))
+
     splitpath = ('/' + '/'.join(head_parts), tail_part)
     collapsed_path = "/".join(splitpath)
 
@@ -947,7 +954,7 @@
         (and the next character is a '/' or the end of the string).
 
         """
-        collapsed_path = _url_collapse_path(urllib.parse.unquote(self.path))
+        collapsed_path = _url_collapse_path(self.path)
         dir_sep = collapsed_path.find('/', 1)
         head, tail = collapsed_path[:dir_sep], collapsed_path[dir_sep+1:]
         if head in self.cgi_directories:
diff -r 089146b8ccc6 Lib/test/test_httpservers.py
--- a/Lib/test/test_httpservers.py	Fri Sep 25 00:49:44 2015 -0400
+++ b/Lib/test/test_httpservers.py	Sat Sep 26 11:46:52 2015 +0800
@@ -425,6 +425,16 @@
                           form.getfirst("bacon")))
 """
 
+cgi_file4 = """\
+#!%s
+import os
+
+print("Content-type: text/html")
+print()
+
+print(os.environ["%s"])
+"""
+
 
 @unittest.skipIf(hasattr(os, 'geteuid') and os.geteuid() == 0,
         "This test can't be run reliably as root (issue #13308).")
@@ -446,6 +456,7 @@
         self.file1_path = None
         self.file2_path = None
         self.file3_path = None
+        self.file4_path = None
 
         # The shebang line should be pure ASCII: use symlink if possible.
         # See issue #7668.
@@ -484,6 +495,11 @@
             file3.write(cgi_file1 % self.pythonexe)
         os.chmod(self.file3_path, 0o777)
 
+        self.file4_path = os.path.join(self.cgi_dir, 'file4.py')
+        with open(self.file4_path, 'w', encoding='utf-8') as file4:
+            file4.write(cgi_file4 % (self.pythonexe, 'QUERY_STRING'))
+        os.chmod(self.file4_path, 0o777)
+
         os.chdir(self.parent_dir)
 
     def tearDown(self):
@@ -499,6 +515,8 @@
                 os.remove(self.file2_path)
             if self.file3_path:
                 os.remove(self.file3_path)
+            if self.file4_path:
+                os.remove(self.file4_path)
             os.rmdir(self.cgi_child_dir)
             os.rmdir(self.cgi_dir)
             os.rmdir(self.parent_dir)
@@ -606,6 +624,13 @@
             (b'Hello World' + self.linesep, 'text/html', HTTPStatus.OK),
             (res.read(), res.getheader('Content-type'), res.status))
 
+    def test_query_with_continuous_slashes(self):
+        res = self.request('/cgi-bin/file4.py?k=aa%2F%2Fbb&//q//p//=//a//b//')
+        self.assertEqual(
+            (b'k=aa%2F%2Fbb&//q//p//=//a//b//' + self.linesep,
+             'text/html', HTTPStatus.OK),
+            (res.read(), res.getheader('Content-type'), res.status))
+
 
 class SocketlessRequestHandler(SimpleHTTPRequestHandler):
     def __init__(self):