CVE-2002-1973 in Badblue
Summary
by MITRE
Buffer overflow in CHttpServer::OnParseError in the ISAPI extension (Isapi.cpp) when built using Microsoft Foundation Class (MFC) static libraries in Visual C++ 5.0, and 6.0 before SP3, as used in multiple products including BadBlue, allows remote attackers to cause a denial of service (access violation and crash) and possibly execute arbitrary code via a long query string that causes a parsing error.
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Analysis
by VulDB Data Team • 08/31/2025
The vulnerability identified as CVE-2002-1973 represents a critical buffer overflow condition within the CHttpServer::OnParseError function of an ISAPI extension component. This flaw specifically manifests when the software is compiled using Microsoft Foundation Class static libraries in Visual C++ versions 5.0 and 6.0 prior to Service Pack 3. The affected ISAPI extension is commonly integrated into various web server products including BadBlue, making this vulnerability particularly widespread in web server environments. The buffer overflow occurs during the processing of malformed query strings that trigger parsing errors, creating a dangerous condition where memory corruption can occur.
The technical nature of this vulnerability stems from improper bounds checking within the ISAPI extension's error handling mechanism. When a malformed query string is processed and triggers the OnParseError function, the code fails to validate the length of input data before copying it into fixed-size buffers. This classic buffer overflow scenario allows attackers to overwrite adjacent memory locations, potentially corrupting program execution flow. The vulnerability specifically targets the Microsoft Foundation Class implementation where static linking creates predictable memory layouts that attackers can exploit. According to CWE standards, this maps to CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflows, though the primary concern here is stack corruption due to the static library usage.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable remote code execution. When exploited, the buffer overflow can cause access violations and system crashes, leading to denial of service conditions that can be particularly damaging in production environments. However, the more serious concern arises from the possibility of arbitrary code execution, which would allow attackers to gain control over the affected system. The vulnerability's exploitability is enhanced by the fact that it requires only a simple HTTP request with a specially crafted query string to trigger the problematic code path. This makes it particularly attractive to attackers as it requires minimal technical sophistication to execute successful attacks against vulnerable systems.
The attack surface for this vulnerability includes any system running the affected ISAPI extension with the vulnerable Microsoft Foundation Class static library configuration. This encompasses various web server implementations that utilize the BadBlue software or similar ISAPI extensions built with the specified Visual C++ versions. The vulnerability demonstrates the risks associated with legacy software development practices and the importance of keeping development environments updated with security patches. Organizations using affected software should consider immediate remediation through patching or upgrading to versions that address the buffer overflow condition in the ISAPI extension implementation. The vulnerability also highlights the need for proper input validation and bounds checking in all network-facing components, as recommended by ATT&CK framework techniques related to command and control communications and execution through system binaries. Security teams should implement monitoring for unusual HTTP request patterns and consider network segmentation to limit the potential impact of successful exploitation attempts.