File resources are not reliably released

Description

Using a file acquired with open() without a with statement or a guaranteed close() call can leak a file descriptor when an exception occurs.

Potential impact

• Repeated requests may exhaust file descriptors and cause denial of service.
• File locks may persist, or temporary-file cleanup may be delayed.

Remediation

• Open files with with open(...) as f:.
• If with cannot be used, ensure that close() runs in a try/finally block.

Examples

Before

handle = open(path)
return handle.read()

After

with open(path) as handle:
    return handle.read()

Explanation:

• Before: The file is opened without a with statement or a guaranteed close() call, so an exception may leave its descriptor open.
• After: Opening the file with with open(...) as f: closes it automatically when the block ends.

References

• CWE-404