CVE-2003-0649 in xpcd
Summary
by MITRE
Buffer overflow in xpcd-svga for xpcd 2.08 and earlier allows local users to execute arbitrary code via a long HOME environment variable.
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Analysis
by VulDB Data Team • 11/26/2024
The vulnerability identified as CVE-2003-0649 represents a critical buffer overflow flaw within the xpcd-svga component of xpcd version 2.08 and earlier. This issue affects systems where the xpcd service is running with elevated privileges, creating a significant security risk for local attackers who can exploit this weakness to gain unauthorized code execution capabilities. The vulnerability specifically targets the handling of the HOME environment variable, which serves as a fundamental system parameter used by various applications to determine user home directory locations and configuration file paths.
The technical implementation of this buffer overflow stems from inadequate input validation within the xpcd-svga module when processing environment variables. When a local user sets an excessively long HOME environment variable, the application fails to properly bounds-check the input data before copying it into a fixed-size buffer. This classic buffer overflow condition occurs because the application assumes a maximum length for the HOME variable without implementing proper sanitization or length validation mechanisms. The flaw exists at the application level where the vulnerable code does not perform adequate memory management checks, allowing attackers to overwrite adjacent memory locations including return addresses and control data structures.
From an operational perspective, this vulnerability presents a severe risk to system integrity as local users can leverage it to execute arbitrary code with the privileges of the xpcd service. Since xpcd typically runs with elevated permissions to manage display server connections and graphics services, successful exploitation could lead to complete system compromise. Attackers could potentially inject malicious code that executes with root privileges, enabling them to modify system files, install backdoors, or establish persistent access to the compromised system. The local nature of this vulnerability means that attackers do not require network access or remote exploitation capabilities, making it particularly dangerous in multi-user environments where privilege escalation is a primary concern.
The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and demonstrates characteristics consistent with attack patterns documented in the MITRE ATT&CK framework under privilege escalation techniques. Specifically, this issue corresponds to T1068, which covers 'Exploitation for Privilege Escalation', and T1059, covering 'Command and Scripting Interpreter'. The exploitation requires local access but provides a pathway for attackers to move laterally within a system or establish persistent access through privilege escalation. Organizations should consider this vulnerability in their risk assessment frameworks, particularly in environments where xpcd services are actively running and where multiple users have local access to systems. The impact extends beyond immediate code execution to include potential data exfiltration, system modification, and establishment of covert communication channels.
Mitigation strategies should include immediate patching of xpcd to version 2.09 or later, which contains the necessary buffer overflow protections. System administrators should also implement environment variable restrictions and monitoring for unusually long HOME variable values. Additional protective measures include disabling unnecessary xpcd services, implementing proper access controls, and conducting regular security audits of system components that handle environment variables. The vulnerability highlights the importance of input validation and proper memory management practices in system-level applications, emphasizing the need for defensive coding techniques and regular security assessments to prevent similar issues from emerging in other components.