CVE-2005-0117 in XShisen
Summary
by MITRE
Buffer overflow in XShisen before 1.36 allows local users to execute arbitrary code via a long GECOS field.
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Analysis
by VulDB Data Team • 06/07/2019
The vulnerability identified as CVE-2005-0117 represents a critical buffer overflow flaw within the XShisen chess game application version 1.35 and earlier. This issue specifically affects the handling of user account information during the login process, where the application fails to properly validate the length of the GECOS field. The GECOS field, a traditional Unix user information field, typically contains comma-separated values including the user's full name, office location, work phone, and home phone. When a local attacker provides an excessively long GECOS field value, the application's buffer handling mechanism becomes overwhelmed, leading to potential memory corruption that can be exploited to execute arbitrary code with the privileges of the affected user.
This buffer overflow vulnerability falls under the CWE-121 category of stack-based buffer overflow, where insufficient bounds checking allows data to overwrite adjacent memory locations. The flaw occurs during the authentication process when XShisen attempts to parse and store user information from the GECOS field into a fixed-size buffer. The vulnerability is particularly concerning because it requires only local user access to exploit, making it accessible to any user with login privileges on the system. The attack vector involves crafting a specially formatted GECOS field entry that exceeds the allocated buffer size, causing a stack overflow condition that can be manipulated to redirect program execution flow.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can potentially allow attackers to execute malicious code with elevated privileges. The exploitation typically involves overwriting the return address on the stack or other critical program variables, enabling the attacker to inject and execute shellcode. Given that XShisen is a graphical application running under the X Window System, successful exploitation could lead to complete system compromise if the application is running with elevated privileges or if the attacker can leverage the vulnerability to gain access to additional system resources. This vulnerability also demonstrates the importance of proper input validation in all user-facing applications, particularly those that interface with system-level authentication mechanisms.
Mitigation strategies for this vulnerability primarily focus on immediate software updates to version 1.36 or later, which contains the necessary patches to address the buffer overflow condition. System administrators should also implement proper access controls and monitor user account information entries to prevent malicious GECOS field manipulation. The vulnerability aligns with ATT&CK technique T1068, which covers 'Local Privilege Escalation', and demonstrates how seemingly benign input fields can become attack vectors when proper validation is absent. Additionally, this issue underscores the need for comprehensive code review practices that include buffer size validation, particularly in applications that process user-provided data in authentication contexts. Organizations should also consider implementing runtime protections such as stack canaries, address space layout randomization, and non-executable stack protections to reduce the likelihood of successful exploitation even if similar vulnerabilities exist in other applications.