A new security vulnerability has been discovered in Apache Tomcat’s CGI servlet implementation that could allow attackers to bypass configured security constraints under specific conditions.
The vulnerability, designated CVE-2025-46701, was disclosed on May 29, 2025, and affects multiple versions of the popular Java application server.
The flaw stems from improper handling of case sensitivity within Apache Tomcat’s CGI servlet, specifically affecting the pathInfo component of URLs mapped to the CGI servlet.
When Tomcat operates on case-insensitive file systems with security constraints configured for the pathInfo component, specially crafted URLs can circumvent these protective measures.
Security researchers have classified this vulnerability as low severity, though it represents a significant concern for organizations relying on CGI-based applications with strict access controls.
The vulnerability particularly impacts environments where CGI support is enabled, which is disabled by default in Tomcat installations.
Apache Tomcat CGI Servlet Vulnerability
The vulnerability affects a broad range of Apache Tomcat versions across three major release branches. Impacted versions include Apache Tomcat 11.0.0-M1 through 11.0.6, 10.1.0-M1 through 10.1.40, and 9.0.0-M1 through 9.0.104.
This extensive range means that numerous production environments could potentially be vulnerable, particularly those that have enabled CGI support for legacy applications or specific development workflows.
The Apache Software Foundation has emphasized that this vulnerability only affects systems where CGI support has been explicitly enabled, as this functionality remains disabled by default across all Tomcat versions.
Organizations using Tomcat primarily for standard web application hosting without CGI functionality are not exposed to this particular attack vector.
The Apache Software Foundation has released patched versions addressing this vulnerability across all affected branches. Organizations should upgrade to Apache Tomcat 11.0.7, 10.1.41, or 9.0.105, depending on their current deployment.
These updated versions include proper case sensitivity handling within the CGI servlet implementation.
The vulnerability was responsibly disclosed by security researcher Greg K, whose GitHub profile indicates expertise in security research. This discovery underscores the importance of continuous security assessment of widely-deployed software components, even for features that may not be commonly utilized in production environments.
System administrators should immediately assess their Tomcat deployments to determine if CGI support is enabled and whether security constraints are applied to pathInfo components.
Organizations using CGI functionality should prioritize upgrading to the patched versions, while those not requiring CGI support should ensure it remains disabled as an additional security measure.
Regular security audits and staying current with vendor security advisories remain critical practices for maintaining secure Apache Tomcat deployments in enterprise environments.
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