What is Signal Handler Race Condition (CWE-364)?

TL;DR: Signal Handler Race Condition (CWE-364) occurs when a signal handler introduces a race condition, allowing an attacker to potentially execute arbitrary code or cause data corruption.

At-a-Glance Table

What is Signal Handler Race Condition?

Signal Handler Race Condition (CWE-364) is a type of vulnerability that occurs when a signal handler introduces a race condition. As defined by the MITRE Corporation under CWE-364, and classified by the OWASP Foundation as not directly mapped.

Quick Summary

Signal Handler Race Condition (CWE-364) is a type of vulnerability that can potentially allow an attacker to execute arbitrary code or cause data corruption by modifying global variables or data structures at unexpected times. This occurs when a signal handler introduces a race condition, which can be caused by the product using a signal handler that is not designed to handle concurrent execution.

Jump to: Quick Summary · Signal Handler Race Condition Overview · How Signal Handler Race Condition Works · Business Impact of Signal Handler Race Condition · Signal Handler Race Condition Attack Scenario · How to Detect Signal Handler Race Condition · How to Fix Signal Handler Race Condition · Framework-Specific Fixes for Signal Handler Race Condition · How to Ask AI to Check Your Code for Signal Handler Race Condition · Signal Handler Race Condition Best Practices Checklist · Signal Handler Race Condition FAQ · Vulnerabilities Related to Signal Handler Race Condition · References · Scan Your Own Site

Signal Handler Race Condition Overview

What: Signal Handler Race Condition (CWE-364) is a type of vulnerability that occurs when a signal handler introduces a race condition.

Why it matters: This can potentially allow an attacker to execute arbitrary code or cause data corruption by modifying global variables or data structures at unexpected times.

Where it occurs: This occurs in Unix-like systems, Linux, macOS, and Windows.

Who is affected: Applications that use signal handlers to perform complex functionality are affected.

Who is NOT affected: Applications that do not use signal handlers or only use them for simple flag-setting operations are not affected.

How Signal Handler Race Condition Works

Root Cause

The root cause of Signal Handler Race Condition (CWE-364) is the product using a signal handler that introduces a race condition.

Attack Flow

1. An attacker sends a signal to the application.
2. The signal handler interrupts code that is executing with privileges.
3. The signal handler may be executed with elevated privileges, allowing the attacker to execute arbitrary code or cause data corruption.

Prerequisites to Exploit

• The product uses a signal handler that introduces a race condition.
• The signal handler is not designed to handle concurrent execution.
• An attacker can send a signal to the application.

Vulnerable Code

void sig_handler(int signum) {
    // Perform complex functionality here...
}

This code demonstrates a vulnerable signal handler that performs complex functionality, introducing a race condition.

Secure Code

void sig_handler(int signum) {
    // Only set flags here...
    flag = 1;
}

This code demonstrates a secure signal handler that only sets flags, avoiding the introduction of a race condition.

Business Impact of Signal Handler Race Condition

Confidentiality: Data corruption can occur when global variables or data structures are modified at unexpected times.

Integrity: Arbitrary code execution can occur when an attacker executes malicious code with elevated privileges.

Availability: The application may crash or exit unexpectedly, causing downtime and loss of productivity.

Some real-world business consequences include:

• Financial losses due to data corruption or arbitrary code execution.
• Compliance issues due to failure to protect sensitive data.
• Reputation damage due to public disclosure of vulnerabilities.

Signal Handler Race Condition Attack Scenario

1. An attacker sends a signal to the application using a tool like kill -9.
2. The signal handler interrupts code that is executing with privileges, allowing the attacker to execute arbitrary code or cause data corruption.
3. The attacker executes malicious code, causing data corruption or arbitrary code execution.

How to Detect Signal Handler Race Condition

Manual Testing

• Use a debugger to step through the signal handler and observe its behavior.
• Use a tool like strace to monitor system calls made by the signal handler.
• Use a tool like gdb to set breakpoints in the signal handler.

Automated Scanners (SAST/DAST)

Static analysis tools can catch some instances of Signal Handler Race Condition, but dynamic analysis is required to detect all cases. Dynamic analysis tools can simulate signals being sent to the application and observe its behavior.

PenScan Detection

PenScan’s automated scanner engines actively test for this issue, helping you identify and fix vulnerabilities before an attacker does.

False Positive Guidance

Be cautious when interpreting results from static or dynamic analysis tools, as some false positives may occur. Verify that the signal handler is indeed introducing a race condition by manually testing the application.

How to Fix Signal Handler Race Condition

• Only use reentrant functions within signal handlers.
• Use validation to ensure that state is consistent while performing asynchronous actions that affect the state of execution.

Framework-Specific Fixes for Signal Handler Race Condition

C/C++

void sig_handler(int signum) {
    // Only set flags here...
    flag = 1;
}

This code demonstrates a secure signal handler in C/C++.

How to Ask AI to Check Your Code for Signal Handler Race Condition

Review the following C/C++ code block for potential CWE-364 Signal Handler Race Condition vulnerabilities and rewrite it using only reentrant functions within signal handlers:

void sig_handler(int signum) {
    // Perform complex functionality here...
}

Signal Handler Race Condition Best Practices Checklist

✅ Use a language that does not allow this weakness to occur or provides constructs that make it easier to avoid. ✅ Design signal handlers to only set flags, rather than perform complex functionality.

Signal Handler Race Condition FAQ

How do I prevent Signal Handler Race Condition?

Use a language that does not allow this weakness to occur or provides constructs that make it easier to avoid. Design signal handlers to only set flags, rather than perform complex functionality.

What is the root cause of Signal Handler Race Condition?

The product uses a signal handler that introduces a race condition.

How does Signal Handler Race Condition work?

A signal handler interrupts code that is executing with privileges, potentially allowing the signal handler to also be executed with elevated privileges.

What are the consequences of Signal Handler Race Condition?

It may be possible to cause data corruption and possibly execute arbitrary code by modifying global variables or data structures at unexpected times.

How do I detect Signal Handler Race Condition?

Use manual testing, automated scanners (SAST/DAST), PenScan detection, and false positive guidance.

How do I fix Signal Handler Race Condition?

Only use reentrant functions within signal handlers. Also, use validation to ensure that state is consistent while performing asynchronous actions that affect the state of execution.

What are some best practices for preventing Signal Handler Race Condition?

Design signal handlers to only set flags, rather than perform complex functionality. Use a language that does not allow this weakness to occur or provides constructs that make it easier to avoid.

Vulnerabilities Related to Signal Handler Race Condition

References

• MITRE CWE-364
• CAPEC
• 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 Signal Handler Race Condition and other risks before an attacker does.