CVE-1999-0847 in FICS Program
Summary
by MITRE
Buffer overflow in free internet chess server (FICS) program, xboard.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability identified as CVE-1999-0847 represents a critical buffer overflow condition within the free internet chess server program known as xboard. This particular flaw manifests in the handling of input data during network communications, where the program fails to properly validate the length of incoming data before copying it into fixed-size memory buffers. The buffer overflow occurs when the xboard application processes commands or data received from network connections without adequate bounds checking mechanisms. This vulnerability specifically affects the chess server software that was widely used in the late 1990s for online chess gaming and communication. The flaw enables remote attackers to potentially execute arbitrary code on systems running vulnerable versions of the software, as the overflow can overwrite critical memory locations including return addresses and program control structures. This type of vulnerability falls under the common weakness enumeration CWE-121, which categorizes buffer overflow conditions that occur when insufficient bounds checking allows data to be written beyond the allocated buffer boundaries.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it creates opportunities for complete system compromise when exploited successfully. Attackers can leverage the buffer overflow to inject malicious code into the memory space of the xboard process, potentially gaining unauthorized access to the underlying system. The vulnerability is particularly concerning because it affects network services that were commonly exposed to the internet, making them prime targets for exploitation. When a remote attacker sends specially crafted input to the vulnerable xboard service, the buffer overflow can result in program termination, memory corruption, or more dangerously, code execution with the privileges of the affected service. The attack surface is broad as xboard was used in various chess server implementations and could be accessed by multiple users simultaneously, amplifying the potential impact of exploitation. This vulnerability aligns with ATT&CK technique T1203, which describes exploitation of software vulnerabilities for privilege escalation and system compromise.
Mitigation strategies for CVE-1999-0847 require immediate attention through software patching and system hardening measures. Organizations should prioritize updating to patched versions of xboard that implement proper input validation and bounds checking mechanisms. The fix typically involves implementing proper buffer size validation before data copying operations and using safer programming practices such as strncpy instead of strcpy functions. Network segmentation and firewall rules should be implemented to restrict access to chess server services only to trusted networks and users. Additionally, monitoring systems should be deployed to detect unusual network traffic patterns that might indicate exploitation attempts. Regular security audits of legacy systems running vulnerable software are essential, particularly in environments where older chess server implementations continue to operate. The vulnerability demonstrates the importance of input validation in network services and serves as a reminder that even seemingly benign applications can contain critical security flaws when proper software development practices are not followed. Implementing proper software security training for developers and establishing secure coding standards can prevent similar vulnerabilities from emerging in future software releases.