CVE-2002-0843 in HTTP Server
Summary
by MITRE
Buffer overflows in the ApacheBench benchmark support program (ab.c) in Apache before 1.3.27, and Apache 2.x before 2.0.43, allow a malicious web server to cause a denial of service and possibly execute arbitrary code via a long response.
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Analysis
by VulDB Data Team • 09/13/2025
The vulnerability identified as CVE-2002-0843 represents a critical buffer overflow flaw within the ApacheBench benchmark utility, commonly referred to as ab.c, which was part of the Apache HTTP Server software. This security weakness affected Apache versions prior to 1.3.27 and Apache 2.x versions before 2.0.43, creating a significant risk for systems utilizing this benchmarking tool. The flaw specifically manifests in how the ab.c program processes HTTP responses from web servers, making it susceptible to exploitation by malicious actors who control the target web server.
The technical implementation of this vulnerability stems from inadequate input validation within the ApacheBench utility's response handling mechanism. When the benchmark tool receives HTTP responses from a web server, it attempts to parse and store response data in fixed-size buffers without proper bounds checking. This programming oversight allows an attacker controlling the web server to craft malicious responses containing excessive data that exceeds the allocated buffer space. The buffer overflow occurs when the program writes more data into the allocated memory buffer than it can accommodate, leading to memory corruption that can be exploited to execute arbitrary code or cause system instability.
From an operational perspective, this vulnerability creates severe implications for system security and availability. The attack vector requires the malicious web server to be in a position to influence the response data that ApacheBench processes, typically occurring when the benchmark tool is used against a target server that the attacker controls or has access to. The potential impact includes complete system compromise through code execution, denial of service conditions that prevent legitimate users from accessing services, and possible data corruption within the affected system. This vulnerability directly maps to CWE-121, which describes heap-based buffer overflow conditions, and aligns with ATT&CK technique T1499.004 for denial of service attacks.
The exploitation of this vulnerability typically involves crafting HTTP responses with oversized headers or content that triggers the buffer overflow condition in the ab.c program. When ApacheBench processes such malformed responses, the memory corruption can lead to unpredictable behavior including program crashes, memory corruption, or potentially full system compromise if the attacker can control the execution flow. The vulnerability is particularly concerning because ApacheBench is commonly used for performance testing and load evaluation, making it a frequently employed tool that could be targeted by attackers seeking to disrupt legitimate testing activities or gain unauthorized system access.
Mitigation strategies for CVE-2002-0843 primarily involve upgrading to patched versions of Apache HTTP Server, specifically Apache 1.3.27 or later, and Apache 2.0.43 or later. Organizations should also implement network segmentation to limit access to ApacheBench utilities and avoid using them against untrusted web servers. Additionally, administrators should disable or restrict the use of ApacheBench in environments where the target servers cannot be fully trusted. The vulnerability demonstrates the importance of proper input validation and memory management practices in security-critical applications, aligning with security best practices outlined in various industry standards including those from the Open Web Application Security Project and the Center for Internet Security. Regular security assessments and vulnerability scanning should be conducted to identify and remediate similar buffer overflow conditions in other software components that may be susceptible to similar attacks.