Improper Input Validation in Apache Tomcat Affects Multiple Versions

CVE-2026-24733

What is CVE-2026-24733?

CVE-2026-24733 is a vulnerability found in Apache Tomcat, a widely-used open-source application server that enables developers to run Java Servlets and render web pages using Java Server Pages (JSP). This vulnerability arises from improper input validation concerning HTTP/0.9 requests, particularly regarding the handling of GET and HEAD requests. Specifically, it allows an attacker to bypass security constraints configured to restrict access based on request methods. When certain configurations deny GET requests but permit HEAD requests, the flaw can be exploited by sending a HEAD request that is technically invalid under the HTTP/0.9 specification. This can lead to unauthorized access to restricted resources, effectively undermining the integrity of web applications deployed on Apache Tomcat.

The versions affected by CVE-2026-24733 include Apache Tomcat from 11.0.0-M1 to 11.0.14, from 10.1.0-M1 to 10.1.49, and from 9.0.0.M1 to 9.0.112. Organizations using these versions are at risk, particularly if they have implemented security constraints that could be evaded through this vulnerability. The recommended mitigation is to upgrade to fixed versions: 11.0.15 or later, 10.1.50 or later, or 9.0.113 or later.

Potential impact of CVE-2026-24733

1. Unauthorized Access: The primary impact of CVE-2026-24733 is the potential for unauthorized access to sensitive parts of web applications. Attackers could bypass established access controls, leading to the exposure of confidential data or critical system functions that should otherwise be secured.

2. Data Integrity Compromise: By exploiting this vulnerability, an attacker could manipulate or extract data from an application, threatening data integrity. This could result in misleading information being processed or presented to users, undermining trust in the application.

3. Increased Attack Surface: Organizations that continue to use affected versions of Apache Tomcat without applying necessary updates may find themselves increasing their attack surface. As the vulnerability could be exploited by various threat actors, the risk of further compromise escalates, paving the way for more severe attacks such as data breaches or service disruptions.

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