Operating systems have global directories where any user have write access. Those folders are mostly used as temporary storage areas like /tmp in Linux based systems. An application manipulating files from these folders is exposed to race conditions on filenames: a malicious user can try to create a file with a predictable name before the application does. A successful attack can result in other files being accessed, modified, corrupted or deleted. This risk is even higher if the application runs with elevated permissions.

In the past, it has led to the following vulnerabilities:

This rule raises an issue whenever it detects a hard-coded path to a publicly writable directory like /tmp (see complete list bellow). It also detects access to TMP and TMPDIR environment variables.

Ask Yourself Whether

You are at risk if you answered yes to any of those questions.

Recommended Secure Coding Practices

Sensitive Code Example

file = open("/tmp/temporary_file","w+") # Sensitive
tmp_dir = os.environ.get('TMPDIR') # Sensitive
file = open(tmp_dir+"/temporary_file","w+")

Compliant Solution

import tempfile

file = tempfile.TemporaryFile(dir="/tmp/my_subdirectory", mode='"w+") # Compliant

See