CVE-2016-5425 in Tomcat
Summary
by MITRE
The Tomcat package on Red Hat Enterprise Linux (RHEL) 7, Fedora, CentOS, Oracle Linux, and possibly other Linux distributions uses weak permissions for /usr/lib/tmpfiles.d/tomcat.conf, which allows local users to gain root privileges by leveraging membership in the tomcat group.
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Analysis
by VulDB Data Team • 06/29/2024
The vulnerability described in CVE-2016-5425 represents a critical privilege escalation flaw within the Tomcat application server deployment on multiple enterprise Linux distributions including RHEL 7, Fedora, CentOS, and Oracle Linux. This issue stems from improper file system permissions that create an exploitable path for local attackers who possess membership in the tomcat group. The vulnerability specifically targets the /usr/lib/tmpfiles.d/tomcat.conf configuration file which governs temporary file creation and management for the Tomcat service. The weak permissions allow malicious users to modify this critical system configuration file, thereby enabling them to escalate their privileges to root level access.
The technical flaw manifests through a classic path traversal and permission manipulation attack vector where the tomcat group members can leverage their access to the temporary file management system to gain unauthorized root privileges. This occurs because the tmpfiles.d configuration file lacks proper access controls and ownership restrictions that would normally prevent non-root users from modifying system-level configuration files. The vulnerability operates under the principle of least privilege violation where the security model fails to properly isolate the tomcat service from potential privilege escalation attacks. According to CWE classification, this vulnerability maps to CWE-276: Incorrect Permissions for a Resource, which specifically addresses improper access control mechanisms that allow unauthorized users to modify critical system resources.
The operational impact of this vulnerability is severe as it transforms a local user account with tomcat group membership into a root-level attacker capable of executing arbitrary code with full system privileges. Attackers can exploit this weakness to establish persistent backdoors, modify system binaries, access sensitive data, and completely compromise the host system. The attack requires minimal prerequisites since the tomcat group membership is typically granted to legitimate users for service management purposes, making this vulnerability particularly dangerous in enterprise environments where service accounts are commonly configured. The vulnerability also aligns with ATT&CK technique T1068: Exploitation for Privilege Escalation, which describes how adversaries can exploit vulnerabilities to gain elevated privileges.
Mitigation strategies for this vulnerability include immediate remediation through proper file permission configuration where the tomcat.conf file should be owned by root with restrictive permissions set to prevent group or world write access. System administrators should also implement proper access control lists and ensure that the tmpfiles.d directory structure enforces strict ownership policies. Regular security audits should verify that system configuration files maintain appropriate permissions and that no unnecessary group memberships exist that could enable similar privilege escalation paths. The recommended solution involves setting proper file ownership to root:root with permissions of 644 or more restrictive, ensuring that only root users can modify the critical system configuration file that controls temporary file management for the Tomcat service. Organizations should also implement principle of least privilege enforcement and regularly review group memberships to prevent unauthorized access to system-level configuration resources.