CVE-2002-2251 in Lib CGI
Summary
by MITRE
Buffer overflow in the changevalue function in libcgi.h for Marcos Luiz Onisto Lib CGI 0.1 allows remote attackers to execute arbitrary code via a long argument.
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Analysis
by VulDB Data Team • 08/29/2025
The vulnerability identified as CVE-2002-2251 represents a critical buffer overflow flaw within the Marcos Luiz Onisto Lib CGI 0.1 library, specifically within the changevalue function located in the libcgi.h header file. This type of vulnerability falls under the CWE-121 category of Stack-based Buffer Overflow, where insufficient bounds checking allows an attacker to write data beyond the allocated memory space for a buffer. The affected library is commonly used in web applications to handle CGI (Common Gateway Interface) operations, making it a prime target for exploitation in web-based attacks.
The technical implementation of this vulnerability occurs when the changevalue function processes user-supplied input without proper validation of argument length. When a remote attacker submits a specially crafted argument that exceeds the predetermined buffer size, the excess data overflows into adjacent memory locations, potentially corrupting program execution flow. This overflow can overwrite return addresses, function pointers, or other critical program state information, enabling attackers to redirect program execution to malicious code. The vulnerability is particularly dangerous because it operates at the library level, meaning that any application using this CGI library could be compromised through a single vulnerable input point.
The operational impact of CVE-2002-2251 extends beyond simple denial of service scenarios, as it provides remote attackers with the capability to execute arbitrary code on vulnerable systems. This makes it a severe security risk for web applications that rely on the affected library, particularly those handling user input through CGI interfaces. Attackers can leverage this vulnerability to gain unauthorized access to systems, escalate privileges, or establish persistent backdoors. The vulnerability's exploitation requires minimal prerequisites, as it can be triggered through standard web requests, making it highly attractive to automated attack tools and script kiddies. The affected systems may include web servers running CGI applications, web-based content management systems, or any platform utilizing the Marcos Luiz Onisto Lib CGI 0.1 library for processing user interactions.
Mitigation strategies for this vulnerability should prioritize immediate patching of the affected library to version 0.2 or later, which contains the necessary buffer overflow protections and input validation mechanisms. Organizations should implement comprehensive input validation at multiple layers of their application architecture, including application-level filtering and web application firewalls that can detect and block suspicious input patterns. The implementation of stack canaries, address space layout randomization, and non-executable stack protections can provide additional defense-in-depth measures. Security monitoring should include detection of unusual request patterns and parameter lengths that may indicate attempted exploitation. From an ATT&CK framework perspective, this vulnerability maps to techniques involving code injection and privilege escalation, with the attack surface covering web application exploitation and remote code execution phases. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of the vulnerable library within organizational infrastructure, ensuring complete remediation across all affected systems.