112 original_fps = "%s/%s" % (video_track.framerate_original_num, video_track.framerate_original_den)
113 else:
114 original_fps = video_track.original_frame_rate
115 subprocess.check_output([116 "mkvmerge", "--output", out_path,117 "--default-duration", "%d:%sfps" % (video_track.track_id - 1, original_fps),118 file_path119 ], cwd=file_path.parent)120 return out_pathPython possesses many mechanisms to invoke an external executable. If the desired executable path is not fully qualified relative to the filesystem root then this may present a potential security risk.
In POSIX environments, the PATH environment variable is used to specify a set of standard locations that will be searched for the first matching named executable. While convenient, this behavior may allow a malicious actor to exert control over a system. If they are able to adjust the contents of the PATH variable, or manipulate the file system, then a bogus executable may be discovered in place of the desired one. This executable will be invoked with the user privileges of the Python process that spawned it, potentially a highly privileged user.
This test will scan the parameters of all configured Python methods, looking for paths that do not start at the filesystem root, that is, do not have a leading ‘/’ character.
Bad practice
import subprocess
subprocess.run(['calculator', '-u', 'critical', msg], check=True) # Sensitive, Path not qualified from root
Recommended
import subprocess
subprocess.run(['/usr/bin/calculator', '-u', 'critical', msg], check=True) # Path qualified from root
References:
- Bandit B607
- OWASP Top 10 2021 Category A03 - Injection