CVE-2003-0518 in Mac OS X
Summary
by MITRE
The screen saver in MacOS X allows users with physical access to cause the screen saver to crash and gain access to the underlying session via a large number of characters in the password field, possibly triggering a buffer overflow.
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Analysis
by VulDB Data Team • 12/13/2016
The vulnerability described in CVE-2003-0518 represents a critical buffer overflow flaw within the macOS x screensaver implementation that exploits a fundamental security weakness in the operating system's authentication handling mechanisms. This issue specifically targets the screen saver's password validation process where an attacker with physical access to a compromised system can manipulate the password field to trigger a buffer overflow condition. The vulnerability stems from inadequate input validation and memory management within the screensaver component that fails to properly handle excessive character inputs in the password field, creating an exploitable condition that can lead to arbitrary code execution and session access. The flaw exists at the application level within the macOS x screensaver subsystem and demonstrates a classic buffer overflow vulnerability that has been documented under CWE-121 as a weakness involving insufficient restriction of operations within a fixed buffer.
The technical implementation of this vulnerability allows an attacker to input an excessive number of characters into the password field during screen saver activation, which causes the system to exceed allocated buffer boundaries and overwrite adjacent memory locations. This memory corruption can potentially be leveraged to execute malicious code with the privileges of the running screensaver process, which typically operates with elevated permissions. The attack requires only physical access to the target system and does not necessitate network connectivity or remote exploitation capabilities, making it particularly dangerous in environments where physical security controls may be insufficient. The vulnerability operates through a direct memory corruption attack pattern that aligns with ATT&CK technique T1068 which involves the exploitation of a legitimate system process to gain elevated privileges.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable full system compromise when combined with other attack vectors or when executed in conjunction with privilege escalation techniques. An attacker who successfully exploits this vulnerability can gain access to the underlying session, potentially allowing for data exfiltration, persistent access, or further exploitation of other system components. The vulnerability's exploitation is particularly concerning because it occurs during the screen saver activation process, which is a common and expected system behavior that users typically perform without suspicion. This creates a window of opportunity for attackers to gain unauthorized access without alerting users to the compromise. The vulnerability affects the core macOS x security model and demonstrates how seemingly benign user interface components can contain critical security flaws that undermine the overall system security posture.
Mitigation strategies for this vulnerability should focus on immediate patch deployment through official Apple security updates, which would address the underlying buffer overflow condition through proper input validation and memory boundary checking. System administrators should also implement physical security measures including secure workstations, locked rooms, and restricted access controls to prevent unauthorized physical access to systems. Additionally, monitoring for unusual screen saver behavior and implementing security policies that enforce regular password changes and session timeouts can help reduce the attack surface. The vulnerability serves as a reminder of the importance of secure coding practices and input validation, particularly in system components that handle user authentication data, and aligns with industry best practices outlined in secure software development guidelines that emphasize the need for robust buffer management and memory safety mechanisms.