CVE-2005-1025 in AS400
Summary
by MITRE
The FTP server in AS/400 4.3, when running in IFS mode, allows remote attackers to obtain sensitive information via a symlink attack using RCMD and the ADDLNK utility, as demonstrated using the QSYS.LIB library.
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Analysis
by VulDB Data Team • 07/23/2017
The vulnerability described in CVE-2005-1025 represents a critical information disclosure flaw within the AS/400 system's FTP server implementation when operating in Integrated File System (IFS) mode. This vulnerability specifically affects AS/400 version 4.3 and stems from improper handling of symbolic links during remote file access operations. The attack vector involves the exploitation of the Remote Command (RCMD) functionality combined with the ADDLNK utility, which allows unauthorized users to traverse directory structures and access files they should not be able to reach through normal access controls. The vulnerability is particularly concerning because it leverages legitimate system utilities to bypass security boundaries, making detection more challenging and the attack more sophisticated than typical privilege escalation methods.
The technical implementation of this vulnerability resides in the way the AS/400 FTP server processes symbolic links when the system operates in IFS mode. When an attacker uses the ADDLNK utility in conjunction with RCMD commands, they can create or manipulate symbolic links that point to restricted system directories. The QSYS.LIB library serves as the primary target demonstration area where this attack can successfully access sensitive system files and libraries that contain confidential information such as system configurations, user credentials, or proprietary data. This flaw operates at the file system level and directly violates the principle of least privilege by allowing unauthorized access to system resources that should be protected by the operating system's access control mechanisms. The vulnerability specifically relates to CWE-22, which describes improper limitation of a pathname to a restricted directory, and CWE-59, which deals with improper handling of symbolic links.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable more sophisticated attacks within the AS/400 environment. An attacker who successfully exploits this vulnerability could gain access to system configuration files, database definitions, user account information, and potentially sensitive business data stored within the restricted directories. The attack's effectiveness is heightened because it operates through legitimate system interfaces, making it difficult for security monitoring systems to distinguish between normal system operations and malicious activity. This vulnerability could lead to complete system compromise if combined with other attack vectors, as access to system libraries and configuration files often provides attackers with the information needed to plan further exploitation attempts. The impact is particularly severe in enterprise environments where AS/400 systems often serve as core business infrastructure supporting critical applications and data processing functions.
Mitigation strategies for this vulnerability should focus on implementing proper access controls and restricting the use of system utilities that can create symbolic links. Organizations should immediately disable or restrict access to the ADDLNK utility for non-privileged users and implement strict monitoring of RCMD operations. The system should be configured to prevent symbolic link traversal in IFS mode, and access controls should be enforced at multiple levels including network access, file system permissions, and application-level restrictions. Additionally, regular security audits should be conducted to ensure that no unauthorized symbolic links have been created and that the system's file access controls remain properly configured. This vulnerability highlights the importance of following security best practices such as those outlined in the NIST Cybersecurity Framework and aligns with ATT&CK technique T1078 for Valid Accounts and T1566 for Phishing, as the attack leverages legitimate system functionality to gain unauthorized access. System administrators should also consider implementing network segmentation and access control lists to limit exposure and ensure that only authorized personnel can access the affected system components.