Index: Lib/base64.py
===================================================================
--- Lib/base64.py	(revision 74244)
+++ Lib/base64.py	(working copy)
@@ -84,6 +84,8 @@
                             % altchars.__class__.__name__)
         assert len(altchars) == 2, repr(altchars)
         s = _translate(s, {chr(altchars[0]): b'+', chr(altchars[1]): b'/'})
+    if re.search(b'[^A-Za-z0-9/=+\r\n]', s):
+        raise TypeError('Non-base64 digit found: %s' % s)
     return binascii.a2b_base64(s)
 
 
Index: Lib/test/test_base64.py
===================================================================
--- Lib/test/test_base64.py	(revision 74244)
+++ Lib/test/test_base64.py	(working copy)
@@ -137,7 +137,18 @@
         self.assertRaises(TypeError, base64.urlsafe_b64decode, "")
 
     def test_b64decode_error(self):
-        self.assertRaises(binascii.Error, base64.b64decode, b'abc')
+        ar = self.assertRaises
+        ar(binascii.Error, base64.b64decode, b'abc')
+        # Test some invalid characters; addresses [1466065].
+        ar(TypeError, base64.b64decode, b'%3d3LnB5dGhvbi5vcmc=')
+        ar(TypeError, base64.b64decode, b'$3d3LnB5dGhvbi5vcmc=')
+        ar(TypeError, base64.b64decode, b'[3d3LnB5dGhvbi5vcmc=')
+        ar(TypeError, base64.b64decode, b']3d3LnB5dGhvbi5vcmc=')
+        ar(TypeError, base64.b64decode, b'{3d3LnB5dGhvbi5vcmc=')
+        ar(TypeError, base64.b64decode, b'}3d3LnB5dGhvbi5vcmc=')
+        ar(TypeError, base64.b64decode, b'@3d3LnB5dGhvbi5vcmc=')
+        ar(TypeError, base64.b64decode, b'!3d3LnB5dGhvbi5vcmc=')
+        ar(TypeError, base64.b64decode, b'#3d3LnB5dGhvbi5vcmc=')
 
     def test_b32encode(self):
         eq = self.assertEqual