Unexpected working of SUID
Short answer: you haven’t given execute permission to anybody but the file’s owner. The mode is currently 4764. The last two digits have to be 5 or 7 for it to be executable by others.
-
Use 4755.
It’s rare that you want a file to be writable by people other than the owner.
There are cases where you want this,
but the default should be NN44, NN55 or NN11 (or less)
unless you can justify making the file writable.
Setuid files should never never ever be writable by anybody other than the file’s owner.