CVE-1999-0632 in Host
Summary
by MITRE
The RPC portmapper service is running.
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Analysis
by VulDB Data Team • 05/28/2026
The RPC portmapper service represents a fundamental component of the Remote Procedure Call infrastructure that enables distributed computing across networked systems. This service operates on TCP and UDP port 111 and serves as a registry that maps RPC program numbers to network addresses, facilitating communication between client applications and remote services. The presence of this service on a system indicates that the host participates in distributed computing environments and maintains the capability to accept and process RPC requests from remote entities. When this service is actively running without proper security controls, it creates an attack surface that adversaries can exploit to gain unauthorized access to network resources and potentially escalate privileges within the system.
The technical flaw associated with the running RPC portmapper service stems from its inherent design characteristics that prioritize accessibility over security. The service operates with minimal authentication requirements and provides extensive information about available RPC services on the host system. This information disclosure vulnerability allows attackers to enumerate RPC programs and their corresponding network ports, effectively creating a map of potential attack vectors. The service's default configuration often lacks proper access controls, making it susceptible to exploitation through various attack techniques including port scanning, service enumeration, and potential privilege escalation. According to CWE-200, this vulnerability falls under information exposure, where the service inadvertently reveals critical system information that could be leveraged by malicious actors to plan targeted attacks.
The operational impact of an active RPC portmapper service extends beyond simple information disclosure to encompass potential system compromise and network infiltration. Attackers can utilize the information gathered from the portmapper to identify vulnerable RPC services running on the system, including older implementations that may contain unpatched security flaws. The service itself can be targeted through buffer overflow exploits or other vulnerabilities that have been discovered in RPC implementations over the years. This vulnerability aligns with ATT&CK technique T1046, which involves discovery of network services, and T1068, which covers privilege escalation through local exploits. The presence of this service can also facilitate lateral movement within a network as attackers use the information to identify other systems that may be running vulnerable RPC services.
Mitigation strategies for the RPC portmapper service vulnerability require a multi-layered approach that addresses both immediate security concerns and long-term system hardening. The most effective immediate action involves disabling the service entirely if it is not required for system operations, as recommended by the principle of least privilege. When the service must remain active, proper network segmentation should be implemented to restrict access to authorized systems only. The service should be configured with appropriate firewall rules that limit access to port 111 to trusted networks and IP addresses. Additionally, regular security audits should be conducted to ensure that only necessary RPC services are running and that all systems are properly patched against known vulnerabilities. Network monitoring should be implemented to detect unusual RPC activity or unauthorized access attempts to the portmapper service. The implementation of these controls addresses the underlying security weaknesses identified in CWE-284, which deals with improper access control, and helps prevent exploitation techniques outlined in the MITRE ATT&CK framework.