CVE-1999-1528 describes a vulnerability in ProSoft Netware Client version 5.12 running on Macintosh MacOS 9. The issue arises because the client does not automatically log a user out of the Novell Directory Services (NDS) tree when the user logs off the Macintosh system. As a result, the NDS session remains active and accessible on the machine even after the user has logged off. This behavior allows subsequent users of the same Macintosh system to access the previous user's unprotected NDS session without needing to authenticate again. The vulnerability primarily affects the confidentiality and integrity of the NDS session data, as unauthorized users can potentially access sensitive directory information or perform actions under the previous user's credentials. The vulnerability has a CVSS v2 base score of 4.6, indicating a medium severity level. The attack vector is local (AV:L), requiring physical or local access to the affected system. The attack complexity is low (AC:L), and no authentication is required (Au:N) to exploit the vulnerability once local access is obtained. The impact affects confidentiality, integrity, and availability to a partial extent (C:P/I:P/A:P). There is no patch available for this vulnerability, and no known exploits have been reported in the wild. Given the age of the affected software and operating system (MacOS 9), this vulnerability is largely historical but may still be relevant in legacy environments.

For European organizations, the impact of this vulnerability is primarily relevant to those still operating legacy Macintosh systems running MacOS 9 with ProSoft Netware Client 5.12 installed. In such environments, the vulnerability could lead to unauthorized access to NDS directory services, potentially exposing sensitive organizational data or allowing unauthorized directory modifications. This could compromise user credentials, internal directory structures, and access controls managed via NDS. Although the vulnerability requires local access, in shared workstation environments or public access areas, the risk of unauthorized access increases. The inability to automatically log out users from NDS sessions could facilitate insider threats or unauthorized use of directory services, undermining security policies. However, given the obsolescence of the affected platform and software, the overall impact on modern European organizations is limited. Organizations that have migrated to newer directory services or operating systems are unlikely to be affected. Nevertheless, sectors with legacy systems, such as certain industrial, governmental, or archival institutions, may face residual risks.

Since no patch is available for this vulnerability, mitigation must focus on operational and procedural controls. Organizations should: 1) Avoid using ProSoft Netware Client 5.12 on MacOS 9 systems; upgrade to supported clients and modern operating systems where possible. 2) Enforce strict physical security and access controls on Macintosh systems running this software to prevent unauthorized local access. 3) Implement session timeout policies or manual logout procedures to ensure users explicitly log out of NDS sessions before leaving the workstation. 4) Use separate user accounts and restrict shared use of Macintosh systems to minimize risk of session hijacking. 5) Monitor and audit access to legacy systems to detect unauthorized usage. 6) Where legacy systems must remain operational, consider network segmentation to isolate them from critical infrastructure and sensitive data. 7) Educate users about the risks of leaving sessions active and the importance of logging out properly. These measures help reduce the risk of unauthorized access despite the lack of a software patch.