CVE-1999-1279 describes a vulnerability arising from the interaction between the AS/400 shared folders feature and Microsoft SNA Server version 3.0 and earlier (specifically version 2.11). The issue allows users who share the same Local APPC Logical Unit (LU) to view each other's folders. This occurs because the shared folder mechanism in the AS/400 environment, when accessed via Microsoft SNA Server, does not properly isolate user sessions or enforce strict access controls between users sharing the same LU. As a result, unauthorized disclosure of folder contents is possible without authentication or elevated privileges. The vulnerability impacts confidentiality but does not affect integrity or availability. The attack vector is network-based with low attack complexity and no authentication required, making it relatively easy to exploit in environments where these legacy systems are in use. However, this vulnerability dates back to 1999, and no patches are available, likely due to the obsolescence of the affected software versions. There are no known exploits in the wild currently documented.

For European organizations still operating legacy AS/400 systems integrated with Microsoft SNA Server 3.0 or earlier, this vulnerability poses a risk of unauthorized information disclosure. Confidential business data stored in shared folders could be exposed to other users on the same Local APPC LU, potentially leading to data leaks or privacy violations. This could be particularly impactful for industries with strict data protection regulations such as finance, healthcare, and government sectors. Although the vulnerability does not allow modification or destruction of data, the breach of confidentiality could lead to reputational damage, regulatory fines under GDPR, and loss of competitive advantage. Given the age of the vulnerability and the obsolescence of the affected software, the risk is primarily relevant to organizations with legacy infrastructure that has not been modernized or segmented.

Since no official patches are available, mitigation must focus on compensating controls. Organizations should: 1) Identify and inventory all AS/400 and Microsoft SNA Server 3.0 or earlier instances in their environment. 2) Isolate legacy systems on segmented networks with strict access controls to limit user access to shared LUs. 3) Restrict or eliminate the use of shared Local APPC LUs among multiple users to prevent unauthorized folder access. 4) Implement strict user access policies and monitor network traffic for unusual access patterns to shared folders. 5) Plan and execute migration strategies to newer, supported platforms that do not exhibit this vulnerability. 6) Employ encryption and additional authentication layers where possible to protect sensitive data. 7) Conduct regular security audits focusing on legacy system configurations and access controls.