CVE-1999-0411 in OpenServer
Summary
by MITRE
Several startup scripts in SCO OpenServer Enterprise System v 5.0.4p, including S84rpcinit, S95nis, S85tcp, and S89nfs, are vulnerable to a symlink attack, allowing a local user to gain root access.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-0411 represents a critical security flaw in the startup script execution mechanism of SCO OpenServer Enterprise System version 5.0.4p. This issue stems from the improper handling of symbolic links within system initialization scripts that run with elevated privileges during system boot. The affected scripts S84rpcinit, S95nis, S85tcp, and S89nfs all contain susceptible code paths where symbolic link attacks can be exploited to escalate privileges from a local user to root access. The vulnerability specifically manifests when these startup scripts process files or directories that can be manipulated through symbolic link manipulation, creating a path traversal scenario that bypasses normal security controls.
The technical exploitation of this vulnerability follows a classic symlink attack pattern where an attacker creates malicious symbolic links in directories that are processed by the vulnerable startup scripts. When these scripts execute with root privileges during system initialization, they follow the symbolic links and execute attacker-controlled code or overwrite critical system files. This represents a fundamental flaw in privilege separation and file system access control, as the scripts fail to properly validate or resolve symbolic links before processing them. The vulnerability aligns with CWE-367, which describes the improper handling of symbolic links in privileged contexts, and demonstrates how inadequate input validation can lead to privilege escalation. From an operational perspective, this vulnerability allows local attackers to gain complete system control without requiring external network access or complex exploitation techniques, making it particularly dangerous in multi-user environments.
The impact of this vulnerability extends beyond simple privilege escalation as it fundamentally compromises the integrity of the system boot process and the trust model of the operating system. Attackers who successfully exploit this vulnerability can modify critical system files, install backdoors, or manipulate system configurations to maintain persistent access. The attack vector is particularly concerning because it occurs during system startup when the system is in a vulnerable state and the attacker can manipulate the environment before normal security mechanisms are fully operational. This vulnerability also demonstrates weaknesses in the ATT&CK framework's privilege escalation techniques, specifically in the area of "Exploitation for Privilege Escalation" where local attackers can leverage system configuration flaws to gain elevated privileges. The vulnerability's persistence across system reboots makes it particularly dangerous as the attacker can establish a foothold that survives normal system maintenance operations.
Mitigation strategies for this vulnerability require immediate attention to the affected startup scripts and system configuration. The primary remediation involves ensuring that startup scripts properly resolve symbolic links and validate file paths before processing them with elevated privileges. System administrators should implement strict file permissions and directory ownership controls to prevent unauthorized symbolic link creation in critical system directories. The recommended approach includes modifying the vulnerable scripts to explicitly check for symbolic links and refuse processing when they are detected, or using absolute paths instead of relative paths. Additionally, implementing proper file system auditing and monitoring for unauthorized symbolic link creation can help detect exploitation attempts. Organizations should also consider implementing automated patch management processes to ensure that all system components, particularly those related to system initialization and privilege management, are kept up to date with security fixes. The vulnerability highlights the importance of secure coding practices in system-level components and the necessity of validating all input paths in privileged execution contexts.