Looks like there is a bug while trying to decode a non-encode base64 for 12 characters (or multiple of 12) , the return code is always 0.

e.g:- 

1) When trying to decode a encoded value

[vardhaman@oc6085028360 ~]$ echo  'Nzc3Nzk5Cg==' | base64 --decode
777799
[vardhaman@oc6085028360 ~]$ echo $?
0
����base64: invalid input
[vardhaman@oc6085028360 ~]$ echo $?
1

3) Now trying to decode a non-encoded value of 12characters

[vardhaman@oc6085028360 ~]$ echo  'vardhamanbn1' | base64 --decode
��݅�����[vardhaman@oc6085028360 ~]$ echo $?
0

The point 3 should return code as 1 , as invalid input

I feel this bug is present in all version , anywhere sharing the current version where I tested

vardhaman@oc6085028360 ~]$ base64 --version
base64 (GNU coreutils) 8.22
Copyright (C) 2013 Free Software Foundation, Inc.

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