CVE-1999-0078 in Solaris
Summary
by MITRE
pcnfsd (aka rpc.pcnfsd) allows local users to change file permissions, or execute arbitrary commands through arguments in the RPC call.
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Analysis
by VulDB Data Team • 04/16/2026
The vulnerability identified as CVE-1999-0078 affects pcnfsd, also known as rpc.pcnfsd, which is a Network File System daemon that provides compatibility with the older PC-NFS protocol. This daemon operates as an RPC service on Unix systems and handles requests from clients attempting to access files through the Network File System protocol. The flaw exists within the argument processing mechanism of this service, specifically in how it handles input parameters passed through RPC calls. When rpc.pcnfsd receives RPC requests, it fails to properly validate or sanitize the arguments provided by clients, creating a potential attack vector for malicious actors.
The technical nature of this vulnerability stems from inadequate input validation within the RPC processing code of pcnfsd. When remote or local users send RPC calls to the service, they can include specially crafted arguments that manipulate the program's behavior. These malformed arguments can cause the service to execute unintended file permission changes or even arbitrary command execution on the host system. The vulnerability is particularly concerning because it allows attackers to potentially escalate privileges and gain unauthorized access to system resources. The flaw essentially enables a form of command injection where attacker-controlled input directly influences how the service processes file operations, bypassing normal security controls.
From an operational impact perspective, this vulnerability poses significant risks to systems running pcnfsd services. Local users who can access the RPC service can exploit this weakness to modify file permissions, potentially gaining access to restricted files or directories. More critically, the ability to execute arbitrary commands means that attackers could install malicious software, modify system configurations, or even establish persistent backdoors on affected systems. The vulnerability is particularly dangerous in environments where the service runs with elevated privileges, as it could enable complete system compromise. Organizations relying on legacy PC-NFS implementations may face serious security implications, especially in multi-user environments where local access is possible.
Mitigation strategies for this vulnerability should focus on immediate service discontinuation and system hardening. The most effective immediate solution is to disable or remove the rpc.pcnfsd service from affected systems, as the vulnerability exists in a deprecated protocol implementation. System administrators should also consider implementing network segmentation to prevent unauthorized access to RPC services and ensure proper firewall rules are in place to restrict RPC port access. Additionally, upgrading to modern NFS implementations that properly validate input parameters and follow secure coding practices is essential. This vulnerability aligns with CWE-77 and CWE-78 categories related to command injection and improper input validation, and could be mapped to ATT&CK techniques involving privilege escalation and execution through remote services. Organizations should conduct comprehensive audits of their RPC service configurations and ensure that all legacy services are properly deprecated or secured against similar vulnerabilities.