CVE-2000-0307 in OpenServer
Summary
by MITRE
Vulnerability in xserver in SCO UnixWare 2.1.x and OpenServer 5.05 and earlier allows an attacker to cause a denial of service which prevents access to reserved port numbers below 1024.
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Analysis
by VulDB Data Team • 05/29/2018
The vulnerability described in CVE-2000-0307 represents a critical flaw in the xserver implementation of SCO UnixWare 2.1.x and OpenServer 5.05 and earlier versions. This issue stems from improper handling of port reservation mechanisms within the X Window System server component, which forms the foundation of graphical user interfaces in Unix-based operating systems. The vulnerability specifically targets the privileged port range below 1024, which traditionally requires root-level privileges to bind to and access. When exploited, this flaw enables unauthorized users to disrupt normal system operations by preventing legitimate processes from accessing these critical reserved ports.
The technical implementation of this vulnerability resides in the xserver's failure to properly validate or enforce port access controls when attempting to bind to privileged network ports. According to CWE-264, this represents a weakness in permissions, privileges, and access controls that allows attackers to manipulate system resources beyond their intended access levels. The flaw operates by exploiting a race condition or improper input validation within the server's port allocation routines, where the xserver does not adequately verify that only authorized processes can access reserved port numbers. This creates a scenario where malicious actors can effectively block legitimate services from binding to these ports, causing a denial of service condition that impacts the entire graphical interface functionality.
The operational impact of CVE-2000-0307 extends beyond simple service disruption to encompass broader system availability concerns. When attackers can prevent access to reserved ports below 1024, they effectively compromise the ability of critical system services to function properly, particularly those that require elevated privileges to operate. This vulnerability directly aligns with ATT&CK technique T1499.004, which involves network denial of service attacks that target system availability. The implications are particularly severe in multi-user environments where the X server serves as the primary interface for graphical applications, as the disruption can affect multiple concurrent users and prevent essential desktop services from operating correctly. The vulnerability also impacts system administrators who may find themselves unable to restart or maintain critical services that depend on these privileged ports.
Mitigation strategies for CVE-2000-0307 should focus on immediate system hardening and access control enforcement. Organizations should implement proper privilege separation and ensure that only authorized processes can attempt to bind to privileged ports through proper authentication mechanisms. The recommended approach includes applying the vendor-specific patches released by SCO for UnixWare 2.1.x and OpenServer 5.05, which address the underlying port validation logic within the xserver component. Additionally, network administrators should consider implementing firewall rules that restrict access to the X server's network ports and ensure that only trusted hosts can establish connections to the graphical interface services. According to NIST guidelines for system security, this vulnerability requires immediate remediation as it represents a fundamental flaw in the operating system's privilege management that could potentially be exploited to gain further system access. Regular security audits should verify that the xserver configuration properly enforces access controls and that no unauthorized processes can manipulate privileged port bindings.