CVE-2004-1539 in Halo Combat Evolved
Summary
by MITRE
Halo: Combat Evolved 1.05 and earlier allows remote game servers to cause a denial of service (client crash) via a long value in a game server reply, which triggers a NULL dereference.
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Analysis
by VulDB Data Team • 07/14/2025
The vulnerability identified as CVE-2004-1539 represents a critical denial of service flaw affecting Halo: Combat Evolved version 1.05 and earlier. This issue manifests when remote game servers transmit specially crafted responses containing excessively long values during server discovery and connection processes. The flaw specifically targets the client-side parsing mechanism that handles server reply data, creating a condition where malformed input triggers unexpected behavior in the game's networking stack. The vulnerability operates at the application layer of the network stack, exploiting improper input validation within the game's client software that fails to adequately sanitize or limit the length of received server response parameters.
The technical root cause of this vulnerability stems from a NULL pointer dereference condition that occurs when the game client attempts to process server reply data exceeding predetermined length thresholds. When a malicious or compromised server sends a response containing an abnormally long value, the client's parsing routine fails to properly validate the input length before attempting to access memory locations. This results in the program attempting to dereference a null pointer, causing an immediate crash of the client application and termination of the gaming session. The vulnerability falls under CWE-125, which describes out-of-bounds read conditions, and more specifically aligns with CWE-476, pointer dereference without null check, making it a classic example of improper null pointer handling in networked applications.
The operational impact of this vulnerability extends beyond simple service disruption as it enables attackers to remotely compromise the gaming experience for legitimate users. An attacker controlling a malicious game server can repeatedly send malformed responses to clients, causing repeated crashes and making the game unplayable for affected users. This vulnerability particularly affects multiplayer gaming environments where client-server communication is fundamental to gameplay operations. The flaw demonstrates how networked applications can be exploited to cause denial of service conditions without requiring any privileged access or authentication, making it a significant concern for online gaming platforms that rely on third-party server infrastructure. The vulnerability also highlights weaknesses in input validation mechanisms that are crucial for maintaining application stability in distributed network environments.
Mitigation strategies for this vulnerability should focus on implementing robust input validation and length checking mechanisms within the client software. The most effective approach involves modifying the game client to enforce strict limits on server reply data lengths and implement proper null pointer checks before accessing any memory locations. Network administrators should consider implementing server filtering mechanisms that can detect and block suspicious server responses, while game developers should deploy client-side patches that address the specific memory access patterns triggering the vulnerability. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and demonstrates the importance of implementing proper error handling and input validation in networked applications. Organizations should also consider implementing monitoring systems to detect unusual server response patterns that could indicate exploitation attempts, while maintaining up-to-date client software to prevent exploitation of known vulnerabilities in legacy gaming applications.