CVE-2009-0141 in Mac OS X
Summary
by MITRE
XTerm in Apple Mac OS X 10.4.11 and 10.5.6, when used with luit, creates tty devices with insecure world-writable permissions, which allows local users to write to the Xterm of another user.
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Analysis
by VulDB Data Team • 08/27/2019
The vulnerability described in CVE-2009-0141 represents a critical privilege escalation and information disclosure issue affecting Apple Mac OS X versions 10.4.11 and 10.5.6. This flaw specifically manifests when XTerm terminal emulator is used in conjunction with the luit utility, which is designed to handle international character encoding. The core issue lies in the improper permission handling of tty devices created during this interaction, creating a significant security risk within the operating system's user privilege model.
The technical flaw stems from the insecure creation of tty devices with world-writable permissions when XTerm and luit are used together. This configuration allows any local user to write to another user's XTerm session, effectively bypassing the normal security boundaries that should protect user sessions from unauthorized access. The vulnerability operates at the system call level where device file permissions are improperly set, creating a race condition or permission escalation vector. This issue directly maps to CWE-732, which describes improper permission assignment for critical system resources, and aligns with ATT&CK technique T1068 for privilege escalation through local system exploitation.
The operational impact of this vulnerability is substantial as it enables local users to potentially access or manipulate other users' terminal sessions, leading to information disclosure, session hijacking, or execution of malicious commands within another user's context. An attacker could exploit this to capture keystrokes, access sensitive data, or establish persistent access to compromised user sessions. The vulnerability affects the fundamental security model of Mac OS X terminal sessions and could be leveraged in combination with other local exploits to achieve broader system compromise. This weakness particularly impacts multi-user environments where users share the same system and could be exploited by malicious local users or malware operating with user-level privileges.
Mitigation strategies for this vulnerability should focus on immediate system updates and permission hardening measures. Apple released patches for Mac OS X 10.4.11 and 10.5.6 that address the insecure permission handling in the XTerm and luit interaction. System administrators should ensure these patches are applied immediately and monitor for any unauthorized access attempts in user session logs. Additional mitigations include restricting access to the luit utility, implementing proper file permission audits for tty devices, and establishing monitoring for suspicious device file access patterns. The vulnerability also highlights the importance of proper privilege separation and secure coding practices in terminal emulators, particularly regarding device file creation and permission management. Organizations should consider implementing additional logging and monitoring for terminal session activities and user access patterns to detect potential exploitation attempts.