CVE-1999-1279 in SNA Server
Summary
by MITRE
An interaction between the AS/400 shared folders feature and Microsoft SNA Server 3.0 and earlier allows users to view each other's folders when the users share the same Local APPC LU.
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Analysis
by VulDB Data Team • 04/20/2026
The vulnerability described in CVE-1999-1279 represents a significant security flaw in the interoperability between IBM AS/400 systems and Microsoft SNA Server versions 3.0 and earlier. This issue stems from the improper handling of shared folder access controls when multiple users operate under the same Local APPC LU (Local Application Program Control) identifier. The vulnerability specifically affects environments where AS/400 systems utilize shared folders functionality in conjunction with Microsoft SNA Server for network communications and resource sharing.
The technical flaw manifests through a breakdown in access control mechanisms that should normally prevent unauthorized users from accessing shared resources. When multiple users share the same Local APPC LU, the system fails to properly isolate folder access permissions between different user accounts. This creates an unintended privilege escalation scenario where any user within the shared LU context can potentially browse and access folders belonging to other users who share the same logical unit identifier. The vulnerability exploits the trust relationship between the AS/400 shared folders feature and the Microsoft SNA Server, leveraging the shared LU context as an attack vector to bypass normal access controls.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable unauthorized data access and modification. Attackers who can identify users sharing the same Local APPC LU can gain visibility into other users' file systems and potentially access sensitive corporate data, documents, or system resources. This vulnerability particularly affects enterprise environments where AS/400 systems are integrated with Microsoft networking solutions, creating a scenario where legitimate users inadvertently expose their data to unauthorized access through shared network contexts. The risk is compounded in multi-user environments where proper access control segregation has not been properly implemented or maintained.
Organizations affected by this vulnerability should implement immediate mitigations including proper configuration of Local APPC LU assignments to ensure unique identifiers for different user groups, implementation of additional access control layers beyond the default shared folder mechanisms, and network segmentation to isolate critical AS/400 environments from less secure network segments. System administrators should also consider upgrading to Microsoft SNA Server versions that address this specific vulnerability, as well as implementing monitoring solutions to detect unauthorized access attempts. This vulnerability aligns with CWE-284, which describes improper access control in software systems, and maps to ATT&CK technique T1078 for valid accounts and privilege escalation through shared network resources.
The remediation process requires careful assessment of existing Local APPC LU configurations and user access patterns to ensure proper isolation of different user contexts. Network administrators should also review and implement proper authentication and authorization controls that operate independently of the shared folder mechanisms. Regular security audits should verify that no users are inadvertently sharing the same Local APPC LU identifiers, and that appropriate access control policies are enforced at multiple levels of the system architecture. This vulnerability demonstrates the critical importance of proper network segmentation and access control implementation in heterogeneous system environments where multiple vendors' products interact.