CVE-2021-20041 Explained : Impact and Mitigation

A critical vulnerability, CVE-2021-20041, affecting SonicWall SMA100 devices has been discovered recently. This CVE allows an unauthenticated remote attacker to exhaust the device's CPU by sending specially crafted HTTP requests to SMA100 /fileshare/sonicfiles/sonicfiles. The vulnerability could lead to a loop with an unreachable exit condition, impacting SMA 200, 210, 400, 410, and 500v appliances.

Understanding CVE-2021-20041

This section will delve into the nature and impact of the vulnerability in SonicWall SMA100 devices.

What is CVE-2021-20041?

The vulnerability is categorized under CWE-835, indicating a 'Loop with Unreachable Exit Condition,' commonly known as an 'Infinite Loop.' This flaw enables a malicious actor to cause a denial of service by consuming all available CPU resources through a specific HTTP request.

The Impact of CVE-2021-20041

The exploitation of this vulnerability can result in a significant disruption to the affected SonicWall SMA100 appliances, potentially causing service downtime and unavailability.

Technical Details of CVE-2021-20041

In this section, we will explore the technical aspects of CVE-2021-20041 to provide a deeper understanding of the issue.

Vulnerability Description

The vulnerability arises from a flaw in handling HTTP requests by the SMA100 devices, leading to an infinite loop condition that consumes the CPU resources.

Affected Systems and Versions

SonicWall SMA100 devices running versions 9.0.0.11-31sv and earlier, 10.2.0.8-37sv and earlier, 10.2.1.1-19sv and earlier, and 10.2.1.2-24sv and earlier are susceptible to this vulnerability.

Exploitation Mechanism

An unauthenticated malicious actor can exploit this vulnerability remotely by sending crafted HTTP requests to the affected SMA100 devices, triggering the loop condition.

Mitigation and Prevention

This section outlines the steps that organizations and users can take to mitigate the risks associated with CVE-2021-20041 and prevent potential exploitation.

Immediate Steps to Take

Users are advised to apply patches and updates provided by SonicWall to address the vulnerability promptly. Additionally, implementing network security measures to restrict access to vulnerable services can help reduce the risk of exploitation.

Long-Term Security Practices

Regularly monitoring system activity, applying security best practices, and keeping systems up to date with the latest patches are essential for maintaining a secure environment and preventing similar vulnerabilities in the future.

Patching and Updates

Staying informed about security advisories from SonicWall and promptly applying recommended patches and updates can help protect systems from known vulnerabilities.