CVE-2009-2901 in Tomcat
Summary
by MITRE
The autodeployment process in Apache Tomcat 5.5.0 through 5.5.28 and 6.0.0 through 6.0.20, when autoDeploy is enabled, deploys appBase files that remain from a failed undeploy, which might allow remote attackers to bypass intended authentication requirements via HTTP requests.
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Analysis
by VulDB Data Team • 04/29/2026
The vulnerability identified as CVE-2009-2901 affects Apache Tomcat versions ranging from 5.5.0 through 5.5.28 and 6.0.0 through 6.0.20, specifically when the autoDeploy feature is enabled. This security flaw stems from an improper handling of the autodeployment process that occurs during application lifecycle management. The issue manifests when applications are undeployed from the server, but the associated files remain in the appBase directory, creating a persistent security risk that can be exploited by remote attackers.
The technical mechanism behind this vulnerability involves the autodeployment subsystem's failure to properly clean up file resources after an undeployment operation. When autoDeploy is enabled, Tomcat continuously monitors the appBase directory for changes and automatically deploys applications. However, during failed undeployment scenarios, the system does not completely remove all application files, leaving behind remnants that can be accessed through HTTP requests. This creates a condition where unauthorized users can potentially access application components that should have been removed, effectively bypassing authentication mechanisms that were designed to protect these resources.
The operational impact of this vulnerability is significant as it allows remote attackers to gain unauthorized access to application components that should be protected by authentication controls. Attackers can exploit this weakness by crafting HTTP requests that target the lingering application files, potentially accessing sensitive functionality, data, or administrative interfaces that were intended to be removed during the undeployment process. This vulnerability essentially creates a backdoor through which attackers can bypass the normal access control mechanisms that should protect deployed applications.
This vulnerability maps to CWE-22, which describes improper limitation of a pathname to a restricted directory, and also relates to CWE-287, which covers improper authentication. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under T1190 for exploit public-facing applications and T1078 for valid accounts, as attackers can leverage this weakness to access protected resources without proper authentication. The vulnerability demonstrates a critical flaw in application lifecycle management and resource cleanup processes within the web application server environment.
Organizations should implement immediate mitigations including disabling autoDeploy functionality when it is not required, ensuring proper application undeployment processes are followed, and regularly monitoring appBase directories for leftover application files. Additionally, implementing strict access controls, network segmentation, and regular security audits can help reduce the risk of exploitation. System administrators should also consider upgrading to patched versions of Apache Tomcat where this vulnerability has been addressed, as the affected versions have reached end-of-life status and no longer receive security updates. The remediation process should include comprehensive testing of application deployment and undeployment procedures to ensure proper resource cleanup occurs during normal operations.