What is Use of umask() with chmod-style Argument (CWE-560)?

TL;DR: Use of ummask() with chmod-style Argument (CWE-560) is a security vulnerability where incorrect use can lead to improper file permissions, potentially allowing unauthorized access or modification. Fix it by using umask() with the correct argument value.

What is Use of ummask() with chmod-style Argument?

Use of umask() with chmod-style Argument (CWE-560) is a type of security vulnerability that occurs when the product calls umask() with an incorrect argument specified as if it were an argument to chmod(). As defined by the MITRE Corporation under CWE-560, and classified by the OWASP Foundation under [mapping]…

Quick Summary

Use of ummask() with chmod-style Argument is a critical security issue that can lead to improper file permissions being set. This vulnerability arises when an incorrect argument is passed to umask() as if it were intended for chmod(). It matters because such misconfigurations can result in unauthorized access or modification of sensitive files and directories, compromising system integrity and confidentiality.

Jump to: Quick Summary · Use of ummask() with chmod-style Argument Overview · How Use of ummask() with chmod-style Argument Works · Business Impact of Use of ummask() with chmod-style Argument · Use of ummask() with chmod-style Argument Attack Scenario · How to Detect Use of ummask() with chmod-style Argument · How to Fix Use of ummask() with chmod-style Argument · Framework-Specific Fixes for Use of ummask() with chmod-style Argument · How to Ask AI to Check Your Code for Use of ummask() with chmod-style Argument · Use of ummask() with chmod-style Argument Best Practices Checklist · Use of ummask() with chmod-style Argument FAQ · Vulnerabilities Related to Use of ummask() with chmod-style Argument · References · Scan Your Own Site

Use of ummask() with chmod-style Argument Overview

What: A security vulnerability where umask() is called with an incorrect argument intended for chmod().

Why it matters: Incorrect usage can lead to improper file permissions, allowing unauthorized access or modification of files and directories.

Where it occurs: In applications that improperly configure file permissions using umask().

Who is affected: Developers and administrators who manage file permission settings in their code.

Who is NOT affected: Systems where umask() is correctly configured with the appropriate argument values.

How Use of ummask() with chmod-style Argument Works

Root Cause

The root cause lies in incorrect usage of umask() with an argument intended for chmod(), leading to improper file permissions being set.

Attack Flow

1. The application calls umask() with a wrong argument.
2. This results in incorrect permission masks being applied to newly created files or directories.
3. Unauthorized access or modification can occur due to improperly set permissions.

Prerequisites to Exploit

• Application must call umask() incorrectly.
• Files and directories need to be accessible based on the misconfigured permissions.

Vulnerable Code

import os

def create_file():
    os.umask(0o777)  # Incorrect argument for umask()

This code is vulnerable because it sets an incorrect permission mask using umask() with a chmod-style argument, leading to improper file permissions.

Secure Code

import os

def create_file():
    os.umask(0o22)  # Correct argument for umask()

The secure version uses the correct argument value for umask(), ensuring proper permission masks are applied to newly created files or directories.

Business Impact of Use of ummask() with chmod-style Argument

Confidentiality

• Data exposure: Unauthorized access to sensitive files and directories.
• Example: An attacker can read confidential data due to improperly set permissions.

Integrity

• File modification: Unauthorized changes to system files or user data.
• Example: Malicious actors may modify critical configuration files, leading to system instability.

Availability

• Disruption of services: Denial of service through file manipulation.
• Example: An attacker can delete essential system files, disrupting normal operations.

Business Consequences:

• Financial losses due to downtime and recovery efforts.
• Compliance violations from unauthorized access to sensitive data.
• Reputation damage from security breaches affecting customer trust.

Use of ummask() with chmod-style Argument Attack Scenario

1. The application calls umask() incorrectly with a chmod-style argument.
2. This results in improper file permissions being set for newly created files or directories.
3. An attacker identifies the misconfigured permission settings and exploits them to gain unauthorized access.
4. Unauthorized read/write operations are performed on sensitive data, leading to potential data breaches.

How to Detect Use of ummask() with chmod-style Argument

Manual Testing

• Review code for incorrect usage of umask() arguments.
• Verify that the argument passed to umask() is intended for chmod().

Automated Scanners (SAST / DAST)

• Static analysis can detect incorrect umask() calls, but dynamic testing may be required to confirm actual impact.

PenScan Detection

PenScan’s scanner engines like ZAP and Wapiti can identify misconfigured umask() usage in codebases.

False Positive Guidance

False positives occur when the argument appears risky but is actually safe due to context not visible to the scanner. Ensure that the argument matches umask() documentation for correct usage.

How to Fix Use of ummask() with chmod-style Argument

• Use umask() with the correct argument value as specified in documentation.
• Review and update existing code to ensure proper configuration of file permissions.
• Implement automated checks to prevent incorrect umask() arguments from being used.

Framework-Specific Fixes for Use of ummask() with chmod-style Argument

import os

def create_file():
    os.umask(0o22)  # Correct argument for umask()

This example demonstrates the correct usage of umask() in Python to ensure proper file permissions.

How to Ask AI to Check Your Code for Use of ummask() with chmod-style Argument

Use of ummask() with chmod-style Argument Best Practices Checklist

✅ Review all instances where umask() is called to ensure the argument value matches intended usage. ✅ Update existing code to use the correct argument for umask(). ✅ Implement automated checks to prevent incorrect arguments from being used in future development.

Use of ummask() with chmod-style Argument FAQ

How does the use of umask() with a chmod-style argument lead to security issues?

When umask() is called with an incorrectly specified chmod-style argument, it can result in incorrect file permissions being set.

What are the potential consequences if this vulnerability is exploited?

Exploitation may allow unauthorized read and write access to files or directories, compromising integrity and confidentiality of data.

How does a developer detect Use of umask() with chmod-style Argument in their codebase?

Developers can manually review code for incorrect usage of umask() arguments or use automated tools like PenScan to identify the issue.

What is the primary fix technique recommended by experts to prevent this vulnerability?

The primary fix involves using umask() with the correct argument as specified in the documentation.

How does Use of umask() with chmod-style Argument impact different frameworks and platforms?

This issue can affect various programming languages and environments, requiring specific fixes for each technology stack.

What are some best practices to prevent this vulnerability from occurring during development?

Developers should follow secure coding guidelines and regularly review code for potential security weaknesses like incorrect umask() usage.

How does Use of umask() with chmod-style Argument relate to other common vulnerabilities?

access_control_mechanism

Vulnerabilities Related to Use of ummask() with chmod-style Argument

References

• MITRE
• NVD

Scan Your Own Site

Manual code review catches what you know to look for. An automated scan catches what you didn’t. Scan your own website using PenScan to find Use of ummask() with chmod-style Argument and other risks before an attacker does.