Busybox Su Must Be Suid To Work Properly ^hot^ -

The SUID bit is a special file permission that allows a program to run with the privileges of the rather than the current user.

The BusyBox source code explicitly checks for SUID. Inside loginutils/su.c , there is logic similar to: busybox su must be suid to work properly

Use the chmod command to add the +s (setuid) bit. chmod 4755 /bin/busybox (Note: 4755 sets the SUID bit and grants read/execute permissions to others.) 3. Check Mount Options The SUID bit is a special file permission

For embedded systems, avoid BusyBox’s su altogether. Use sudo or a dedicated su binary from a standard package. If you must use BusyBox, ensure the su applet runs with SUID – but be aware of the security trade-offs. chmod 4755 /bin/busybox (Note: 4755 sets the SUID

With great power comes great responsibility. Always audit your SUID binaries, restrict access to su to trusted groups, and consider whether sudo or doas might serve your use case more flexibly. But if you need a tiny, functional su on a BusyBox system, set that SUID bit—and test it thoroughly.