CVE-2021-26690 : What You Need to Know

Apache HTTP Server versions 2.4.0 to 2.4.46 are affected by a vulnerability where a specially crafted Cookie header handled by mod_session can cause a NULL pointer dereference and crash, potentially leading to a Denial of Service (DoS).

Understanding CVE-2021-26690

This section provides an overview of the CVE-2021-26690 vulnerability.

What is CVE-2021-26690?

CVE-2021-26690 is a vulnerability in Apache HTTP Server versions 2.4.0 to 2.4.46 that allows a specially crafted Cookie header to trigger a NULL pointer dereference in mod_session, leading to a potential DoS attack.

The Impact of CVE-2021-26690

The impact of CVE-2021-26690 includes the possibility of crashing the server by exploiting the NULL pointer dereference, which could result in a Denial of Service condition.

Technical Details of CVE-2021-20657

In this section, we delve into the technical aspects of the CVE-2021-26690 vulnerability.

Vulnerability Description

The vulnerability arises from how Apache HTTP Server handles specially crafted Cookie headers in mod_session, resulting in a NULL pointer dereference that could lead to a server crash.

Affected Systems and Versions

Affected versions range from 2.4.0 to 2.4.46 of the Apache HTTP Server, impacting a wide range of systems that have the vulnerable mod_session module.

Exploitation Mechanism

Exploiting this vulnerability involves sending a maliciously crafted Cookie header to the server, triggering the NULL pointer dereference in mod_session and causing a crash.

Mitigation and Prevention

This section outlines the steps to mitigate and prevent the CVE-2021-26690 vulnerability.

Immediate Steps to Take

Users are advised to update their Apache HTTP Server installations to version 2.4.47 or apply patches provided by the vendor to address the mod_session NULL pointer dereference vulnerability.

Long-Term Security Practices

To enhance server security, ongoing monitoring, regular updates, and robust access control mechanisms should be implemented to prevent exploits targeting vulnerabilities like CVE-2021-26690.

Patching and Updates

Regularly check for security advisories from Apache Software Foundation and apply patches promptly to protect systems from known vulnerabilities like CVE-2021-26690.