CVE-2005-2509 in Mac OS X
Summary
by MITRE
unknown vulnerability in loginwindow in mac os x 10.4.2 and earlier when fast user switching is enabled allows attackers to log into other accounts if they know the passwords to at least two accounts.
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Analysis
by VulDB Data Team • 07/04/2025
The vulnerability identified as CVE-2005-2509 represents a critical authentication flaw within the loginwindow component of Mac OS X version 10.4.2 and earlier systems. This issue specifically manifests when fast user switching functionality is enabled, creating a scenario where malicious actors can exploit the system's authentication mechanism to gain unauthorized access to alternative user accounts. The vulnerability stems from insufficient validation of user credentials during the fast user switching process, allowing an attacker with knowledge of two valid account passwords to potentially bypass normal authentication boundaries.
This technical flaw operates at the operating system level within the loginwindow service, which manages user session transitions and authentication contexts. The vulnerability is classified under CWE-284 as an improper access control issue, specifically related to insufficient privileges during user switching operations. When fast user switching is active, the system should maintain strict isolation between user sessions, but this vulnerability allows credential leakage or bypass mechanisms that enable cross-account access. The attack vector is particularly concerning because it requires minimal prerequisites - simply knowing two valid passwords from different accounts is sufficient to exploit the weakness.
The operational impact of CVE-2005-2509 extends beyond simple unauthorized access, as it fundamentally compromises the integrity of the multi-user security model implemented in Mac OS X. An attacker can leverage this vulnerability to escalate privileges, access sensitive user data, modify files, or execute arbitrary commands within other user contexts. This represents a significant threat to organizations relying on multi-user systems, as it undermines the basic security principle that user sessions should remain isolated and secure from one another. The vulnerability affects the core authentication infrastructure and can be exploited remotely or locally, depending on system configuration and network access.
Mitigation strategies for this vulnerability require immediate system updates to Mac OS X versions that address the loginwindow authentication flaw. System administrators should disable fast user switching functionality on systems where it is not essential, as this removes the attack surface entirely. Additionally, implementing strong password policies and regular credential rotation can help reduce the risk of exploitation, though these measures do not address the underlying system flaw. The vulnerability also highlights the importance of proper access control implementation in operating system components, aligning with ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting. Organizations should conduct thorough security assessments of their multi-user systems and ensure that all systems are updated to patched versions that resolve this specific authentication bypass vulnerability.