CVE-2000-0286 in Linux
Summary
by MITRE
X fontserver xfs allows local users to cause a denial of service via malformed input to the server.
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Analysis
by VulDB Data Team • 11/10/2024
The vulnerability identified as CVE-2000-0286 resides within the X fontserver xfs component of the X Window System, a critical networking protocol for graphical user interfaces in Unix-like operating systems. This flaw represents a classic denial of service vulnerability that exploits the server's handling of malformed input data, specifically targeting the font server's processing capabilities. The X fontserver serves as a centralized repository for font resources, enabling multiple X clients to access shared font data efficiently while maintaining a consistent visual appearance across different applications and systems.
The technical mechanism of this vulnerability stems from insufficient input validation within the xfs server implementation. When the server receives malformed font data or improperly formatted requests, it fails to properly sanitize or reject these inputs before processing them. This lack of robust input validation creates a condition where local users can craft specially designed font requests or data packets that trigger unexpected behavior in the server's parsing routines. The flaw typically manifests through buffer overflows, invalid memory access patterns, or stack corruption that occurs during the interpretation of malformed font descriptors or font file structures. According to CWE classification, this vulnerability maps to CWE-121, which encompasses buffer overflow conditions, and CWE-122, which addresses buffer overflow vulnerabilities in heap-based memory structures.
The operational impact of CVE-2000-0286 extends beyond simple service disruption, as it represents a fundamental security weakness that local attackers can exploit without requiring elevated privileges. Since the vulnerability is accessible to any local user account, it creates an attack surface that can be leveraged by malicious insiders or compromised user accounts to systematically degrade system availability. The denial of service effect can range from temporary server unresponsiveness to complete server crashes requiring manual restart, potentially disrupting graphical interface functionality for all users on affected systems. This vulnerability particularly impacts environments where the X fontserver is actively running and serving font requests, which includes most Unix and Linux systems with graphical desktop environments, making it a significant concern for enterprise and server deployments.
Mitigation strategies for this vulnerability encompass both immediate patching and architectural defenses. The primary solution involves applying the official security patches released by the X Window System maintainers, which typically include enhanced input validation routines and proper error handling for malformed font data. System administrators should also implement network segmentation to limit local access to font servers where possible, and consider running the fontserver with reduced privileges or in restricted execution environments. From an ATT&CK framework perspective, this vulnerability aligns with techniques categorized under T1499, which covers network denial of service attacks, and T1068, which addresses local privilege escalation through service manipulation. Organizations should also consider implementing monitoring solutions to detect unusual font server activity patterns that might indicate exploitation attempts, particularly in environments where font servers are exposed to untrusted local users. The vulnerability serves as a reminder of the importance of input validation in network services and demonstrates how seemingly minor flaws in protocol implementations can create significant availability risks for critical system components.