CVE-2002-0517 in OpenUnix
Summary
by MITRE
Buffer overflow in X11 library (libX11) on Caldera Open UNIX 8.0.0, UnixWare 7.1.1, and possibly other operating systems, allows local users to gain root privileges via a long -xrm argument to programs such as (1) dtterm or (2) xterm.
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Analysis
by VulDB Data Team • 06/20/2024
The vulnerability described in CVE-2002-0517 represents a critical buffer overflow flaw within the X11 library implementation on specific Unix operating systems including Caldera Open UNIX 8.0.0 and UnixWare 7.1.1. This issue stems from inadequate input validation in the X11 library's handling of command-line arguments, specifically the -xrm option which is used to specify X resource manager resources. The flaw occurs when programs utilizing libX11 such as dtterm and xterm process excessively long -xrm arguments without proper bounds checking, creating a condition where memory allocated for storing these arguments can be overwritten beyond its intended boundaries.
The technical exploitation of this vulnerability relies on the fundamental principle of buffer overflow attacks where an attacker can manipulate the program's memory layout to execute arbitrary code with elevated privileges. When a local user provides a crafted long -xrm argument to programs like dtterm or xterm, the X11 library fails to validate the length of the input string before copying it into a fixed-size buffer. This buffer overflow can overwrite adjacent memory locations including return addresses on the stack, allowing an attacker to redirect program execution flow and potentially execute malicious code with the privileges of the targeted program. The vulnerability is particularly dangerous because these programs typically run with elevated privileges, especially when invoked by root or in setuid contexts, making the privilege escalation from local user to root possible through this vector.
The operational impact of CVE-2002-0517 extends beyond simple privilege escalation as it represents a fundamental security weakness in the X11 windowing system implementation that affects multiple Unix variants. The attack vector is relatively straightforward since it requires only local access and knowledge of the vulnerable programs, making it exploitable in scenarios where an attacker already has user-level access to the system. The vulnerability affects programs that rely on the X11 library for their graphical interface functionality, particularly those used in terminal emulation and window management. From an attacker's perspective, this represents a low-effort, high-impact method of gaining root access, as the exploitation does not require network connectivity or complex attack chains. The vulnerability is categorized under CWE-121 as a stack-based buffer overflow, which aligns with the memory corruption characteristics observed in this specific implementation flaw.
Mitigation strategies for this vulnerability should focus on immediate patching of the affected X11 library versions, as the primary solution involves updating to patched versions that implement proper input validation and bounds checking. System administrators should also implement additional security measures such as disabling unnecessary X11 applications, implementing proper access controls, and monitoring for suspicious command-line arguments. The vulnerability demonstrates the importance of input validation in system libraries and highlights how seemingly benign features like X resource management can become attack vectors when proper security controls are absent. Organizations should consider implementing privilege separation techniques, using sandboxing mechanisms, and maintaining regular security updates to prevent exploitation of similar buffer overflow vulnerabilities in their Unix environments. This vulnerability also reinforces the necessity of following secure coding practices such as those outlined in the CERT C Secure Coding Standard and aligns with ATT&CK technique T1068 which covers privilege escalation through local exploits, making it a critical component of comprehensive endpoint security strategies.