CVE-1999-1077 is a vulnerability affecting the idle locking function in MacOS 9, an older operating system released by Apple. The vulnerability allows a local attacker to bypass the password protection of an idled session. Specifically, when a MacOS 9 system is locked due to idleness, an attacker with local access can use a particular keyboard sequence—either the programmer's switch or the CMD-PWR key combination—to invoke a debugger. This debugger can then be leveraged to disable the lock mechanism, effectively bypassing the password protection without needing to authenticate. The vulnerability arises from the way MacOS 9 handles idle locking and debugger invocation, allowing unauthorized access to a locked session. The CVSS score assigned is 4.6 (medium severity), reflecting that exploitation requires local access and low attack complexity but results in partial compromise of confidentiality, integrity, and availability. There is no patch available for this vulnerability, and no known exploits have been reported in the wild. Given the age of the affected system (MacOS 9 was released in the late 1990s), this vulnerability is primarily of historical interest or relevant in legacy environments still running this outdated OS.

For European organizations, the impact of this vulnerability is generally low in modern contexts because MacOS 9 is an obsolete operating system no longer supported or used in mainstream environments. However, organizations that maintain legacy systems or specialized equipment running MacOS 9 could be at risk. The vulnerability allows an attacker with physical or local access to bypass session locks, potentially exposing sensitive information or allowing unauthorized changes. This could lead to data confidentiality breaches, unauthorized system modifications, or disruption of availability if the attacker disables security controls. In environments where legacy MacOS 9 systems are used for critical functions, such as in certain industrial, research, or archival contexts, the risk is more pronounced. The lack of a patch means that mitigation relies on compensating controls. Overall, the threat is limited by the requirement for local access and the rarity of MacOS 9 in current European IT infrastructures.

Given the absence of an official patch, European organizations should focus on compensating controls to mitigate this vulnerability. First, restrict physical and local access to any systems running MacOS 9, ensuring that only trusted personnel can interact with these machines. Implement strict physical security measures such as locked rooms or cabinets. Second, consider disabling or restricting the use of the programmer's switch and CMD-PWR keyboard sequences if possible, or configure the system to limit debugger invocation. Third, where feasible, migrate legacy systems from MacOS 9 to modern, supported operating systems to eliminate the vulnerability entirely. Fourth, implement monitoring and auditing of physical access to legacy systems to detect unauthorized attempts to access or manipulate the machines. Finally, educate staff about the risks of legacy systems and enforce policies that minimize their exposure to untrusted users.