CVE-2000-0378 in Linux
Summary
by MITRE
The pam_console PAM module in Linux systems performs a chown on various devices upon a user login, but an open file descriptor for those devices can be maintained after the user logs out, which allows that user to sniff activity on these devices when subsequent users log in.
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Analysis
by VulDB Data Team • 12/05/2024
The vulnerability described in CVE-2000-0378 resides within the pam_console Pluggable Authentication Module implementation on Linux systems, representing a significant security flaw in the authentication and session management framework. This issue specifically affects the handling of device file permissions and ownership during user login and logout processes, creating a persistent security risk that spans multiple user sessions. The vulnerability is particularly concerning because it operates at the system level through the PAM module architecture, which serves as a fundamental component for authentication services across Unix-like operating systems.
The technical flaw manifests when the pam_console module executes a chown system call on various device files during user login, but fails to properly close or invalidate file descriptors associated with these devices. This creates a scenario where even after a user logs out, the file descriptors remain open and accessible to the system. The underlying mechanism involves the module's improper handling of device file access rights and the subsequent lack of proper cleanup procedures that should occur during session termination. When subsequent users log in, the stale file descriptors can still be accessed, allowing the previously logged-out user to potentially monitor or capture data from these devices through the open connections.
The operational impact of this vulnerability extends beyond simple privilege escalation, creating a persistent surveillance capability that can be exploited by malicious users or compromised accounts. Attackers could leverage this flaw to monitor network traffic, capture keystrokes, or access sensitive data from device files that should be restricted to specific user sessions. This vulnerability particularly affects systems where multiple users share the same physical hardware and where device access is not properly isolated between sessions. The security implications are compounded by the fact that this issue operates silently in the background without explicit user notification, making detection and mitigation particularly challenging. The vulnerability directly relates to CWE-284, which addresses improper access control, and aligns with ATT&CK techniques involving privilege escalation and persistence mechanisms. This flaw essentially creates a backdoor through which users can maintain access to device resources even after their session should have ended, undermining the fundamental security assumptions of user session isolation and device access control.
The recommended mitigations for this vulnerability involve immediate patching of the pam_console module and implementation of proper file descriptor management during user session transitions. System administrators should ensure that all device file descriptors are properly closed upon user logout, and that the PAM module implementation includes robust session cleanup procedures. Additionally, implementing proper access controls and monitoring for unauthorized device access can help detect potential exploitation attempts. Organizations should also consider implementing session management policies that enforce stricter device access controls and regular security audits of authentication modules. The vulnerability demonstrates the critical importance of proper resource cleanup in security-sensitive components and highlights the need for comprehensive testing of session management procedures in authentication frameworks.