CVE-2022-39955 : What You Need to Know

A vulnerability has been identified in the OWASP ModSecurity Core Rule Set, allowing bypass of a partial rule set by manipulating the HTTP Content-Type header. This can lead to the evasion of detection mechanisms and potential exploitation of vulnerable back-end systems.

Understanding CVE-2022-39955

This section will provide insights into the nature and impact of the CVE-2022-39955 vulnerability.

What is CVE-2022-39955?

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass when a specially crafted HTTP Content-Type header field is submitted. This header field indicates multiple character encoding schemes, allowing malicious actors to bypass the configurable CRS Content-Type header "charset" allow list. This manipulation can enable encoded payloads to evade detection and be decoded by the backend system.

The Impact of CVE-2022-39955

The vulnerability affects legacy CRS versions 3.0.x and 3.1.x, as well as the currently supported versions 3.2.1 and 3.3.2. Users and integrators are advised to upgrade to versions 3.2.2 and 3.3.3 respectively to mitigate the risk.

Technical Details of CVE-2022-39955

This section will delve into the technical aspects of the CVE-2022-39955 vulnerability.

Vulnerability Description

The vulnerability in OWASP ModSecurity CRS allows for a partial rule set bypass by exploiting the HTTP Content-Type header, facilitating the evasion of detection mechanisms and potential backend system exploitation.

Affected Systems and Versions

OWASP ModSecurity Core Rule Set versions 3.0.x, 3.1.x, 3.2.1, and 3.3.2 are impacted by this vulnerability.

Exploitation Mechanism

By submitting a specially crafted HTTP Content-Type header field, threat actors can manipulate character encoding schemes to bypass CRS detection mechanisms and potentially decode payloads on the backend.

Mitigation and Prevention

In this section, we will discuss the necessary steps to mitigate and prevent the CVE-2022-39955 vulnerability.

Immediate Steps to Take

Users and integrators should upgrade to OWASP ModSecurity CRS versions 3.2.2 or 3.3.3 to address the vulnerability and prevent potential exploitation.

Long-Term Security Practices

Implementing a robust security posture, including regular updates and security monitoring, can help prevent similar vulnerabilities in the future.

Patching and Updates

Stay informed about security advisories and promptly apply patches and updates to ensure the continued security of systems and applications.