CVE-2004-0724 in Half-Life
Summary
by MITRE
The Half-Life engine before July 7 2004 allows remote attackers to cause a denial of service (server or client crash) via an empty fragmented packet.
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Analysis
by VulDB Data Team • 06/18/2018
The vulnerability described in CVE-2004-0724 represents a critical denial of service flaw within the Half-Life engine ecosystem that existed prior to the July 7 2004 update. This vulnerability specifically targets the network packet processing mechanisms employed by the game engine's networking stack, creating a condition where specially crafted empty fragmented packets can trigger system instability. The issue stems from inadequate input validation and packet handling procedures within the engine's network communication layer, which fails to properly account for edge cases involving fragmented data transmission.
The technical implementation of this vulnerability exploits the fundamental way the Half-Life engine processes network fragments during data transmission. When the engine receives a fragmented packet that contains no actual data payload, the processing routine becomes vulnerable to a crash condition. This occurs because the engine's packet reassembly logic does not adequately validate the size or content of fragmented segments before attempting to process them. The flaw operates at the application layer of the network stack, specifically within the engine's UDP packet handling code that manages fragmented data transmission between clients and servers. This type of vulnerability aligns with CWE-129, which addresses issues related to insufficient input validation, and represents a classic example of a buffer over-read condition that can be triggered through malformed packet data.
The operational impact of this vulnerability extends beyond simple service disruption to encompass complete system instability across both client and server environments. When exploited, the vulnerability can cause immediate termination of game sessions, forcing players to disconnect from multiplayer matches and potentially leading to complete server shutdowns that affect entire gaming communities. The remote nature of the attack means that adversaries can trigger these crashes from any location without requiring local access to the affected systems, making it particularly dangerous for online gaming environments where server stability is crucial. This vulnerability directly impacts the availability aspect of the CIA triad by creating conditions that prevent legitimate users from accessing networked gaming services, and it can be leveraged to disrupt gaming experiences at scale across multiple connected systems.
Mitigation strategies for this vulnerability primarily involve implementing proper input validation and packet size checking within the network processing code. The most effective approach requires updating the Half-Life engine to include comprehensive validation of fragment headers and data lengths before attempting to reassemble packets. Security measures should include implementing bounds checking for fragmented packet data, adding proper error handling for empty packet conditions, and ensuring that the engine's networking stack can gracefully handle malformed input without crashing. Organizations should also consider implementing network-level filtering to detect and block suspicious fragmented packet patterns, though this approach provides only partial protection. This vulnerability demonstrates the importance of robust input validation in networked applications and aligns with ATT&CK technique T1498, which covers denial of service attacks targeting network services. The remediation process should also include thorough code review of network handling routines and implementation of automated testing for edge case scenarios involving fragmented data transmission, ensuring that similar vulnerabilities are not present in other network processing components of the software ecosystem.