CVE-2007-6326 in Simple HTTPD
Summary
by MITRE
Sergey Lyubka Simple HTTPD (shttpd) 1.3 on Windows allows remote attackers to cause a denial of service via a request that includes an MS-DOS device name, as demonstrated by the /aux URI.
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Analysis
by VulDB Data Team • 10/12/2024
The vulnerability identified as CVE-2007-6326 affects Sergey Lyubka's Simple HTTPD (shttpd) version 1.3 running on Windows operating systems. This issue represents a denial of service vulnerability that arises from the server's improper handling of specific URI requests containing MS-DOS device names. The exploit demonstrates the use of the /aux URI as a proof of concept, highlighting how the web server fails to properly sanitize input requests before processing them. The root cause lies in the server's lack of proper validation when encountering device names that are reserved in the Windows file system, particularly those that correspond to legacy MS-DOS device names such as aux, con, nul, prn, and others.
The technical flaw stems from insufficient input validation and sanitization within the shttpd server implementation. When a client submits a request containing an MS-DOS device name in the URI path, the server attempts to process this request without proper filtering of these reserved names. Windows operating systems treat these device names as special system resources, and when the web server tries to resolve or process paths containing such names, it can trigger system-level errors or resource exhaustion conditions. This particular vulnerability falls under CWE-20, which describes improper input validation, and specifically relates to CWE-116, which addresses improper encoding or escaping of input data. The vulnerability manifests as a denial of service condition because the server cannot properly handle these malformed requests and typically crashes or becomes unresponsive when encountering such inputs.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of web services running on affected systems. Attackers can exploit this weakness by simply sending a crafted HTTP request containing the /aux URI or similar device name patterns, causing the web server to consume excessive resources or enter an error state. This makes the vulnerability particularly dangerous in production environments where continuous availability is critical. The attack vector is straightforward and requires minimal technical expertise, making it attractive to malicious actors seeking to disrupt web services. Systems running shttpd 1.3 on Windows platforms are vulnerable to this attack, and the impact can be severe as it affects the fundamental availability of the web server service, potentially causing service interruptions that could affect business operations or user access to web applications.
Mitigation strategies for this vulnerability should focus on input validation and sanitization at multiple levels. The primary solution involves updating to a newer version of shttpd that properly handles MS-DOS device names in URI requests, as this vulnerability was likely addressed in subsequent releases. System administrators should implement proper input filtering mechanisms that reject or sanitize requests containing reserved device names before they reach the web server core. Network-level protections such as web application firewalls can be configured to detect and block requests containing MS-DOS device names in URI paths. Additionally, the server should be configured to run with minimal privileges and proper resource limits to prevent complete system compromise. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network denial of service attacks, and T1595.001, which addresses reconnaissance through information discovery. Organizations should also implement monitoring solutions to detect unusual request patterns that might indicate exploitation attempts, and conduct regular security assessments to identify similar input validation weaknesses in other web applications and services.