CVE-2021-42376 Explained : Impact and Mitigation

A NULL pointer dereference in Busybox's hush applet leads to denial of service when processing a crafted shell command. Learn more about the impact, technical details, and mitigation steps.

Understanding CVE-2021-42376

This CVE involves a NULL pointer dereference in Busybox's hush applet, leading to a denial of service under specific conditions.

What is CVE-2021-42376?

The vulnerability stems from missing validation after a \x03 delimiter character in the Busybox hush applet, allowing for a crafted shell command to trigger a denial of service, particularly in scenarios of filtered command input.

The Impact of CVE-2021-42376

Exploitation of the vulnerability can result in a denial of service attack.
The issue is considered critical as it could lead to service disruption or unavailability.

Technical Details of CVE-2021-42376

This section details the vulnerability, affected systems, and the exploitation mechanism.

Vulnerability Description

The NULL pointer dereference in Busybox's hush applet is triggered by processing a crafted shell command, potentially causing DoS.

Affected Systems and Versions

Vendor: busybox
Product: busybox
Affected Version: unspecified, less than 1.34.0

Exploitation Mechanism

The vulnerability can be exploited by sending a crafted shell command containing the \x03 delimiter character, circumventing proper validation and resulting in a NULL pointer dereference.

Mitigation and Prevention

To address CVE-2021-42376, take immediate steps and implement long-term security practices.

Immediate Steps to Take

Update Busybox to version 1.34.0 or later to mitigate the vulnerability.
Monitor and restrict shell command input to prevent malicious exploitation.

Long-Term Security Practices

Conduct regular security audits and code reviews to identify vulnerabilities.
Educate staff on secure coding practices and the importance of input validation.
Implement strong access controls and least privilege principles to limit attack surfaces.

Patching and Updates

Regularly apply security patches provided by Busybox to address known vulnerabilities.