CVE-1999-1230 in Quake Server
Summary
by MITRE
Quake 2 server allows remote attackers to cause a denial of service via a spoofed UDP packet with a source address of 127.0.0.1, which causes the server to attempt to connect to itself.
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Analysis
by VulDB Data Team • 04/17/2026
The vulnerability described in CVE-1999-1230 represents a classic denial of service flaw affecting the Quake 2 game server implementation. This issue stems from the server's inadequate validation of incoming UDP packet sources, specifically failing to properly handle packets originating from the loopback address 127.0.0.1. The flaw exists in the network protocol handling layer where the server processes incoming connection requests without sufficient source address verification, creating a condition where malicious actors can exploit this weakness to disrupt server operations. The vulnerability is particularly concerning as it demonstrates a fundamental lack of input validation in network communication handling, which is a common pattern seen in various network services and applications. This type of vulnerability falls under the category of improper input validation as defined by CWE-20, where the system fails to properly validate or sanitize input data from external sources. The attack vector involves sending a spoofed UDP packet with a source address of 127.0.0.1 to the Quake 2 server, which triggers the server's internal connection logic to attempt establishing a connection to itself. This self-connection attempt creates a resource exhaustion scenario where the server's connection handling mechanisms become overwhelmed, leading to service disruption. The operational impact of this vulnerability extends beyond simple service interruption as it can potentially cause the server to crash or become unresponsive for extended periods, affecting all players attempting to connect to the game. This issue highlights the importance of proper network address validation and the dangers of assuming that incoming packets originate from legitimate sources. The vulnerability is classified as a remote attack since the malicious packet can be sent from any location on the network, requiring no local access or authentication. From an attacker perspective, this represents a low-effort, high-impact method of service disruption that can be executed without significant technical expertise. The flaw demonstrates how simple protocol handling errors can be exploited to create significant operational problems, particularly in gaming environments where server uptime is critical for player experience. This vulnerability also illustrates the importance of implementing proper network security practices and defensive measures such as source address validation and packet filtering. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under the denial of service category, where adversaries leverage system weaknesses to prevent legitimate users from accessing services. The implications of this vulnerability extend to broader network security practices, as it demonstrates how even seemingly minor implementation flaws can create substantial service availability issues. Network administrators and system operators should consider this type of vulnerability when implementing security controls, particularly in environments where network services are exposed to untrusted networks. The remediation approach for this specific vulnerability would involve implementing proper source address validation within the Quake 2 server code, ensuring that packets originating from loopback addresses are properly handled or rejected. Additionally, network-level filtering can be implemented to prevent spoofed packets from reaching the server, providing an additional layer of protection against this type of attack. The vulnerability serves as a reminder of the critical importance of secure coding practices and the need for comprehensive input validation in network-facing applications.