CVE-1999-1077 in Mac OS
Summary
by MITRE
Idle locking function in MacOS 9 allows local attackers to bypass the password protection of idled sessions via the programmer's switch or CMD-PWR keyboard sequence, which brings up a debugger that the attacker can use to disable the lock.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-1077 represents a critical security flaw in the Macintosh operating system version 9 that fundamentally undermines the integrity of the system's session protection mechanisms. This issue stems from an insufficiently implemented idle locking function that creates an exploitable backdoor through legitimate system debugging interfaces. The vulnerability specifically affects the MacOS 9 operating environment where the standard idle timeout mechanism fails to properly secure user sessions, leaving them susceptible to unauthorized access through well-known keyboard sequences.
The technical implementation of this flaw involves the programmer's switch functionality and the CMD-PWR keyboard combination that are designed for legitimate debugging purposes but are improperly secured within the system's authentication framework. When users activate these sequences, they gain access to a system debugger that operates outside the normal security boundaries of the operating system. This debugger interface provides attackers with direct access to system functions that can be used to disable or bypass the idle lock mechanism entirely. The vulnerability essentially creates a race condition between the system's idle detection and the debugger's access permissions, allowing an attacker to manipulate system state while the lock is active.
From an operational perspective, this vulnerability presents a significant risk to organizations relying on MacOS 9 for their computing needs, particularly in environments where sensitive data is processed or stored. The attack vector is particularly concerning because it requires no specialized tools or knowledge beyond basic keyboard input, making it accessible to even novice attackers. The exploitation process allows unauthorized individuals to maintain access to locked sessions without having to bypass complex authentication mechanisms, effectively rendering the idle lock feature useless for its intended security purpose. This vulnerability directly impacts the confidentiality and integrity of system data, as attackers can access protected information and potentially modify system configurations.
The security implications of this vulnerability align with CWE-284, which addresses improper access control mechanisms, and can be mapped to ATT&CK technique T1068, which covers local privilege escalation through system debugging interfaces. Organizations affected by this vulnerability should implement immediate mitigations including disabling the programmer's switch functionality, modifying keyboard mappings to prevent access to the CMD-PWR sequence, and ensuring that system administrators are aware of the specific attack vectors available through these debugging interfaces. Additionally, implementing regular security audits to verify that idle locking mechanisms function properly and that debugging interfaces are appropriately restricted would help prevent exploitation of this vulnerability.
The remediation strategy should prioritize system updates to newer versions of the MacOS operating system where these issues have been addressed through improved access control mechanisms and better integration between system security features and debugging interfaces. Organizations should also consider implementing additional security measures such as automated session management policies, enhanced logging of keyboard input sequences, and regular security assessments to identify potential exploitation vectors. The vulnerability demonstrates the importance of considering all potential access points to system security features, including legitimate debugging interfaces that may be misused if not properly secured against unauthorized access.