CVE-1999-0406 in Unix
Summary
by MITRE
Digital Unix Networker program nsralist has a buffer overflow which allows local users to obtain root privilege.
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Analysis
by VulDB Data Team • 04/18/2026
The vulnerability identified as CVE-1999-0406 resides within the Digital Unix Networker program nsralist, a component of the Digital Unix operating system that manages network resources and file sharing operations. This buffer overflow vulnerability represents a critical security flaw that can be exploited by local users to escalate their privileges to the root level, fundamentally compromising the system's security model. The Digital Unix operating system, developed by Digital Equipment Corporation, was widely used in enterprise environments during the late 1990s and early 2000s, making this vulnerability particularly concerning for organizations running legacy systems.
The technical flaw in nsralist stems from improper input validation and buffer management within the program's code structure. When the program processes certain input parameters, it fails to properly check the length of user-supplied data before copying it into fixed-size buffers. This classic buffer overflow condition occurs because the program does not implement bounds checking or size validation mechanisms that would prevent excessive data from overwriting adjacent memory locations. The vulnerability specifically manifests when local users provide crafted input to the nsralist command, which then gets processed without adequate sanitization, allowing malicious data to overwrite stack memory and potentially overwrite return addresses or other critical program variables.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally undermines the security architecture of Digital Unix systems. Local users who can execute the nsralist program gain the ability to execute arbitrary code with root privileges, effectively providing them with complete system control. This includes the capability to modify system files, create new user accounts, install malware, and bypass all other security controls. The vulnerability is particularly dangerous because it requires minimal privileges to exploit, as users only need local access to the system to attempt the attack. This makes it a preferred target for both malicious insiders and external attackers who have gained initial access to the system, as it provides a straightforward path to achieving maximum system compromise.
The exploitation of this vulnerability aligns with several ATT&CK framework techniques including privilege escalation through exploitation of software vulnerabilities and execution through local commands. From a CWE perspective, this represents a classic CWE-121: Stack-based Buffer Overflow, which is categorized under the broader class of CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer. Organizations running Digital Unix systems should implement immediate mitigations including applying vendor patches, disabling unnecessary services, and implementing strict access controls to limit local user privileges. The vulnerability also underscores the importance of proper input validation and memory management practices in system development, as outlined in security standards such as the OWASP Top Ten and NIST Cybersecurity Framework, which emphasize the need for robust defensive programming techniques to prevent such memory corruption vulnerabilities from being exploited in production environments.