CVE-2008-6704 in S.T.A.L.K.E.R.: Shadow of Chernobyl
Summary
by MITRE
Integer overflow in the NET_Compressor::Decompress function in S.T.A.L.K.E.R.: Shadow of Chernobyl 1.0006 and earlier allows remote attackers to cause a denial of service (server crash) via a crafted packet with a 0xc1 value that contains no compressed data, which triggers a copy of a large amount of memory.
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Analysis
by VulDB Data Team • 12/09/2017
The vulnerability identified as CVE-2008-6704 represents a critical integer overflow flaw within the networking compression functionality of S.T.A.L.K.E.R.: Shadow of Chernobyl version 1.0006 and earlier. This issue resides in the NET_Compressor::Decompress function which handles incoming network packets destined for the game server. The flaw manifests when processing specially crafted network packets that contain a 0xc1 value in their header without any actual compressed data payload. This specific packet structure triggers a miscalculation in the decompression routine where the system attempts to allocate and copy an extraordinarily large amount of memory based on malformed size parameters. The vulnerability operates at the intersection of memory management and network protocol handling, creating a scenario where legitimate network traffic can be exploited to exhaust server resources through improper memory allocation.
The technical exploitation of this vulnerability leverages fundamental flaws in integer arithmetic handling within the decompression logic. When the 0xc1 value is encountered, the system interprets this as a valid compression header but fails to properly validate the associated size parameters. This leads to a scenario where a small packet header can cause the decompression routine to attempt copying memory regions that are orders of magnitude larger than the actual packet data. The integer overflow occurs during the calculation of buffer sizes needed for decompression, where the result exceeds the maximum representable value for the integer type used, causing wraparound behavior that results in an unexpectedly large memory allocation request. This type of vulnerability falls under the CWE-190 category for integer overflow and aligns with ATT&CK technique T1499.004 for network denial of service attacks.
The operational impact of this vulnerability extends beyond simple server crashes to potentially compromise the entire game service availability. When exploited, the vulnerability causes the target server to allocate massive amounts of memory, leading to system resource exhaustion and subsequent service disruption. This denial of service condition affects all players connected to the vulnerable server, rendering the game unplayable and potentially impacting server performance for other services running on the same infrastructure. The vulnerability is particularly concerning in multiplayer gaming environments where server stability directly affects user experience and game economy. The exploit requires minimal network sophistication to execute, making it an attractive target for malicious actors seeking to disrupt gaming services. The memory allocation behavior can also potentially trigger memory fragmentation issues, compounding the denial of service effects and making system recovery more challenging.
Mitigation strategies for this vulnerability must address both immediate patching requirements and longer-term architectural improvements to prevent similar issues. The most effective immediate solution involves applying the official patch released by the game developers to correct the integer overflow in the decompression routine. Organizations should also implement network-level filtering to identify and block packets containing the specific 0xc1 header pattern before they reach vulnerable servers. Additional defensive measures include implementing memory allocation limits and monitoring systems that can detect unusual memory usage patterns indicative of this exploit. Network administrators should consider implementing rate limiting and connection validation mechanisms to reduce the effectiveness of such attacks. The vulnerability highlights the importance of proper input validation and integer overflow protection in networked applications, emphasizing the need for comprehensive security testing of all network handling code. Organizations running similar legacy gaming servers should conduct thorough vulnerability assessments to identify other potential integer overflow conditions in their network processing code, as this type of flaw can often be found in older software systems that lack modern security hardening practices.