CVE-2016-5018 in Tomcat
Summary
by MITRE
In Apache Tomcat 9.0.0.M1 to 9.0.0.M9, 8.5.0 to 8.5.4, 8.0.0.RC1 to 8.0.36, 7.0.0 to 7.0.70 and 6.0.0 to 6.0.45 a malicious web application was able to bypass a configured SecurityManager via a Tomcat utility method that was accessible to web applications.
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Analysis
by VulDB Data Team • 09/29/2022
The vulnerability identified as CVE-2016-5018 represents a critical security flaw in Apache Tomcat versions spanning multiple release branches including 9.0.0.M1 through M9, 8.5.0 through 8.5.4, 8.0.0.RC1 through 8.0.36, 7.0.0 through 7.0.70, and 6.0.0 through 6.0.45. This issue fundamentally undermines the security model of the application server by allowing malicious web applications to circumvent configured security restrictions through improper access to internal utility methods. The flaw specifically targets the SecurityManager implementation within Tomcat's architecture, which is designed to enforce security policies and prevent unauthorized access to system resources. When properly configured, the SecurityManager should act as a barrier between web applications and the underlying operating system, preventing malicious code from accessing sensitive functionality such as file system operations, network connections, or system calls that could compromise server integrity.
The technical implementation of this vulnerability stems from a design oversight where certain utility methods within Tomcat's internal codebase remained accessible to web applications despite being intended for internal use only. These methods, when invoked by malicious applications, provide pathways to bypass the SecurityManager's enforcement mechanisms and gain unauthorized access to system resources. The flaw operates at the level of method accessibility and privilege separation, where the boundary between trusted internal components and untrusted web application code becomes porous. This vulnerability is particularly dangerous because it allows attackers to escalate privileges and execute arbitrary code with the permissions of the Tomcat process, potentially leading to complete server compromise. The issue manifests as a failure in the security model implementation where access controls that should prevent web applications from invoking sensitive internal methods are circumvented through the exploitation of legitimate but improperly restricted interfaces.
The operational impact of CVE-2016-5018 extends far beyond simple privilege escalation, as it fundamentally compromises the isolation between web applications running on the same Tomcat instance. Attackers can leverage this vulnerability to access system files, execute arbitrary commands, and potentially establish persistent backdoors on affected servers. This vulnerability directly violates the principle of least privilege and undermines the security boundaries that separate different applications and prevent cross-application attacks. The implications are severe for multi-tenant hosting environments where multiple applications share the same Tomcat instance, as a single compromised application could potentially compromise the entire server. Organizations running affected versions of Tomcat face significant risk of data breaches, service disruption, and potential regulatory compliance violations. The vulnerability's presence in multiple major release branches means that organizations across different Tomcat versions needed to urgently implement remediation measures to protect their infrastructure.
This vulnerability maps to CWE-284 Access Control Issues, specifically related to improper access control mechanisms where insufficient checks allow unauthorized access to protected resources. From an ATT&CK framework perspective, this vulnerability enables techniques such as privilege escalation and defense evasion, allowing adversaries to move laterally within the system and maintain persistence. The remediation strategy requires immediate patching of affected Tomcat versions to the latest stable releases where the SecurityManager implementation has been properly hardened. Organizations should also implement additional security controls such as application firewalls, runtime monitoring, and regular security assessments to detect potential exploitation attempts. The vulnerability highlights the importance of proper security boundary enforcement in application servers and the critical need for thorough access control testing during security reviews. System administrators must ensure that all web applications deployed on Tomcat instances are properly sandboxed and that the SecurityManager is correctly configured to prevent unauthorized access to internal system resources. Regular security updates and vulnerability assessments remain essential practices to protect against similar flaws in application server implementations.