CVE-2021-33037 : Vulnerability Insights and Analysis

Apache Tomcat 10.0.0-M1 to 10.0.6, 9.0.0.M1 to 9.0.46, and 8.5.0 to 8.5.66 are affected by a vulnerability due to incorrect parsing of the HTTP transfer-encoding request header, leading to the possibility of request smuggling when used with a reverse proxy. The issue was reported by security researchers from NEU seclab. This CVE was published on July 12, 2021, by the Apache Tomcat Security Team.

Understanding CVE-2021-33037

This section provides an in-depth look at the impact, technical details, and mitigation strategies related to CVE-2021-33037.

What is CVE-2021-33037?

CVE-2021-33037 is a security vulnerability in Apache Tomcat versions 8.5.0 to 8.5.66, 9.0.0.M1 to 9.0.46, and 10.0.0-M1 to 10.0.6 that mishandles the HTTP transfer-encoding request header, potentially allowing for request smuggling attacks in certain scenarios.

The Impact of CVE-2021-33037

The vulnerability in Apache Tomcat could be exploited to perform request smuggling attacks when the affected versions are used in conjunction with a reverse proxy. This could lead to unauthorized access or information disclosure.

Technical Details of CVE-2021-33037

This section delves into the specifics of the vulnerability, including its description, affected systems, and exploitation mechanism.

Vulnerability Description

Apache Tomcat did not correctly parse the HTTP transfer-encoding request header in certain situations, which could result in request smuggling. The issue arose from how Tomcat handled different encoding scenarios, potentially allowing malicious actors to perform smuggling attacks.

Affected Systems and Versions

The vulnerability impacts Apache Tomcat versions 8.5.0 to 8.5.66, 9.0.0.M1 to 9.0.46, and 10.0.0-M1 to 10.0.6. Users operating these versions are advised to take immediate action to mitigate the risk.

Exploitation Mechanism

The vulnerability stems from improper handling of the HTTP transfer-encoding header, where Tomcat inconsistently processed encoding declarations, leaving room for attackers to manipulate requests and potentially carry out request smuggling attacks.

Mitigation and Prevention

In response to CVE-2021-33037, users and administrators should adopt immediate and long-term security measures to safeguard their systems from potential exploitation.

Immediate Steps to Take

It is crucial to update Apache Tomcat to a secure version that addresses the parsing issue in the HTTP transfer-encoding header. Additionally, users should monitor for any suspicious activity that may indicate an ongoing attack.

Long-Term Security Practices

To enhance overall system security, consider implementing robust security protocols, conducting regular vulnerability assessments, and staying informed about the latest security advisories.

Patching and Updates

Stay informed about security updates and patches released by Apache Software Foundation for Apache Tomcat. Timely patching of software vulnerabilities is essential to mitigate the risk of exploitation and maintain a secure environment.