CVE-2006-0228 in grsecurity
Summary
by MITRE
The RBAC functionality in grsecurity before 2.1.8 does not properly handle when the admin role creates a service and then exits the shell without unauthenticating, which causes the service to be restarted with the admin role still active.
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Analysis
by VulDB Data Team • 01/11/2019
The vulnerability identified as CVE-2006-0228 resides within the grsecurity kernel security module, specifically affecting versions prior to 2.1.8. This issue demonstrates a critical flaw in the Role-Based Access Control implementation that undermines the fundamental security principles of privilege management and session handling. The grsecurity module, designed to enhance Linux kernel security through various mechanisms including mandatory access controls, RBAC systems, and kernel hardening features, fails to properly terminate administrative privileges when users exit shell sessions without explicit logout procedures. This weakness creates a persistent security risk where elevated privileges remain active even after the user has seemingly ended their session.
The technical flaw manifests when an administrator with the admin role creates a service within the system and subsequently exits the shell environment without performing proper authentication deactivation. Under normal circumstances, when a user exits a shell session, the system should automatically revoke all active privileges and clean up the session context. However, grsecurity's RBAC implementation does not adequately handle this specific scenario, leading to a situation where the service continues running with administrative privileges. This behavior constitutes a privilege escalation vulnerability because the service maintains elevated access rights even though the original administrative user has terminated their session. The flaw stems from improper session cleanup mechanisms and inadequate privilege isolation between user sessions and background services.
The operational impact of this vulnerability extends beyond simple privilege persistence, creating potential attack vectors for malicious actors who might exploit the lingering administrative privileges. An attacker who gains access to a system with administrative credentials could potentially maintain persistent access through services that continue operating with elevated privileges even after the user has logged out. This vulnerability directly violates the principle of least privilege and could enable attackers to perform unauthorized system modifications, escalate privileges further, or maintain backdoor access. The persistent nature of the elevated privileges makes detection more difficult and increases the potential damage that can be achieved through prolonged unauthorized access. This issue particularly affects systems where administrators frequently create and manage services, as the vulnerability becomes more prevalent in environments with active administrative activity.
Mitigation strategies for CVE-2006-0228 involve immediate upgrading of grsecurity to version 2.1.8 or later, where the proper session cleanup mechanisms have been implemented. System administrators should also implement additional monitoring and logging of service creation and privilege usage to detect anomalous behavior. The vulnerability aligns with CWE-284, which addresses improper access control in software implementations, and relates to ATT&CK technique T1068, which covers privilege escalation through service exploitation. Organizations should conduct comprehensive security audits of their grsecurity configurations and ensure that proper session management procedures are enforced. Regular patch management processes should be implemented to address similar vulnerabilities in kernel security modules, and system administrators should be trained on proper session termination procedures to minimize exposure to this class of vulnerability. The fix implemented in grsecurity 2.1.8 addresses the root cause by ensuring that administrative privileges are properly revoked when shell sessions terminate, regardless of whether the user explicitly logs out or simply exits the shell environment.