CVE-2023-35855 in Counter-Strike
Summary
by MITRE • 06/19/2023
A buffer overflow in Counter-Strike through 8684 allows a game server to execute arbitrary code on a remote client's machine by modifying the lservercfgfile console variable.
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Analysis
by VulDB Data Team • 01/11/2026
The vulnerability identified as CVE-2023-35855 represents a critical buffer overflow flaw within the Counter-Strike gaming framework through version 8684. This security weakness specifically targets the game server's ability to manipulate client-side execution through the lservercfgfile console variable, creating a potential attack vector that could allow remote code execution on affected client machines. The flaw exists at the intersection of client-server communication protocols and memory management within the gaming engine, making it particularly dangerous for multiplayer environments where servers may be compromised or untrusted.
The technical implementation of this vulnerability stems from inadequate input validation and bounds checking when processing the lservercfgfile console variable. When a malicious game server modifies this variable with excessively long input data, the system fails to properly validate the length of the provided string before copying it into a fixed-size buffer allocated in memory. This classic buffer overflow condition occurs because the application does not verify that the input data fits within the allocated buffer space, allowing attackers to overwrite adjacent memory locations including return addresses, function pointers, or other critical program state information. The vulnerability aligns with CWE-121, which categorizes buffer overflow conditions that occur when insufficient bounds checking allows data to be written beyond the boundaries of allocated memory regions.
The operational impact of CVE-2023-35855 extends beyond simple remote code execution to encompass full system compromise of affected clients. An attacker who gains control of a game server or can influence server configuration parameters can leverage this vulnerability to execute arbitrary code on any client machine that connects to the compromised server. This threat model particularly affects multiplayer gaming environments where users trust server administrators and may not be aware of the potential for malicious server configurations. The vulnerability creates a persistent risk for players who participate in public or semi-public gaming sessions, as the attack can be initiated simply by connecting to a malicious server that modifies the lservercfgfile variable to contain malicious input data.
Mitigation strategies for this vulnerability must address both immediate defensive measures and long-term architectural improvements. Players should avoid connecting to untrusted or unknown game servers until patches are available, as the vulnerability can be exploited through legitimate gameplay scenarios. Game server administrators should implement strict input validation for console variables and monitor for unusual modifications to configuration parameters. The security community should also consider implementing runtime protections such as stack canaries, address space layout randomization, and data execution prevention mechanisms to reduce the exploitability of similar buffer overflow conditions. From an ATT&CK framework perspective, this vulnerability maps to techniques involving command and control communications, remote service execution, and privilege escalation through exploitation of software vulnerabilities, making it a significant concern for both gaming security and broader cybersecurity operations.