CVE-1999-1225 in HP-UX
Summary
by MITRE
rpc.mountd on Linux, Ultrix, and possibly other operating systems, allows remote attackers to determine the existence of a file on the server by attempting to mount that file, which generates different error messages depending on whether the file exists or not.
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Analysis
by VulDB Data Team • 10/20/2025
The vulnerability identified as CVE-1999-1225 affects the rpc.mountd service across multiple operating systems including Linux and Ultrix, representing a significant information disclosure weakness in network file sharing protocols. This flaw resides within the Network File System (NFS) implementation where the rpc.mountd daemon handles mount requests from clients, creating an avenue for attackers to perform reconnaissance through systematic file existence testing. The vulnerability stems from the service's inconsistent error handling behavior when processing mount requests for files, effectively leaking information about the target system's file structure without proper authentication or authorization checks.
The technical mechanism behind this vulnerability operates through the NFS mount protocol's response differentiation based on file existence conditions. When a remote attacker attempts to mount a file using rpc.mountd, the service generates distinct error messages depending on whether the target file exists or not. This behavior creates a timing-based information leakage channel where attackers can systematically test file paths and observe the different responses to infer the presence or absence of specific files on the server. The flaw essentially transforms the mount service from a legitimate file sharing mechanism into a reconnaissance tool for directory enumeration, as demonstrated through the differential error responses that reveal file system structure to unauthorized parties.
The operational impact of CVE-1999-1225 extends beyond simple information disclosure, as it provides attackers with valuable intelligence for subsequent exploitation phases. An attacker who successfully identifies the existence of sensitive files through this vulnerability can then prioritize their attack vectors, focusing on known files that might contain credentials, configuration data, or other valuable assets. This reconnaissance capability directly aligns with the attack technique described in the MITRE ATT&CK framework under initial access and reconnaissance phases, where adversaries gather information about target systems before executing more sophisticated attacks. The vulnerability also contributes to the broader category of information leakage that can facilitate privilege escalation and lateral movement within networked environments.
The security implications of this vulnerability are particularly concerning given the widespread use of NFS in enterprise environments and the fundamental nature of the flaw in the mount daemon's error handling. Organizations running affected systems face the risk of unauthorized file enumeration across their network shares, potentially exposing sensitive directories and files that should remain hidden from external inspection. This issue represents a classic case of insufficient input validation and error handling, which maps to CWE-200 (Information Exposure) and CWE-20 (Improper Input Validation) in the Common Weakness Enumeration catalog. The vulnerability demonstrates how seemingly benign service responses can create security risks when they provide differential feedback based on system state conditions without proper access controls.
Mitigation strategies for CVE-1999-1225 require a multi-layered approach focusing on both immediate service hardening and broader network security controls. System administrators should implement proper network segmentation to limit access to NFS services, ensuring that only authorized clients can reach the affected rpc.mountd service. The use of firewall rules to restrict NFS ports and implement access control lists can significantly reduce the attack surface. Additionally, organizations should consider upgrading to newer versions of NFS implementations that address this information disclosure weakness, as many modern implementations have improved error handling that does not provide differential responses based on file existence. The implementation of network monitoring solutions to detect unusual mount request patterns can also serve as an early warning system for potential exploitation attempts, aligning with defensive techniques described in the ATT&CK framework for threat detection and response activities.