CVE-2001-0731 in HTTP Server
Summary
by MITRE
Apache 1.3.20 with Multiviews enabled allows remote attackers to view directory contents and bypass the index page via a URL containing the "M=D" query string.
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Analysis
by VulDB Data Team • 10/04/2025
The vulnerability identified as CVE-2001-0731 represents a significant security flaw in Apache HTTP Server version 1.3.20 that exploits the Multiviews feature to disclose directory contents and circumvent access controls. This vulnerability specifically targets the configuration where the Multiviews option is enabled, allowing attackers to manipulate URL parameters to gain unauthorized access to directory listings and bypass default index page restrictions. The flaw stems from how Apache processes the "M=D" query string parameter within the context of Multiviews functionality, creating an unintended information disclosure channel that can reveal sensitive directory structures and files.
The technical implementation of this vulnerability leverages Apache's content negotiation mechanisms that are designed to handle multiple representations of resources. When Multiviews is enabled, Apache attempts to determine the best content representation based on various factors including the client's preferences and server configuration. However, the specific handling of the "M=D" parameter creates a pathway where attackers can manipulate the URL to request directory listings in a manner that bypasses normal access controls. This occurs because the Multiviews module does not properly validate or sanitize the query string parameters, allowing the attacker to inject directives that alter the directory traversal behavior. The vulnerability manifests when Apache processes the request and interprets the "M=D" parameter as a directive to display directory contents rather than honoring standard access restrictions.
The operational impact of CVE-2001-0731 extends beyond simple information disclosure, as it provides attackers with a method to bypass security controls and potentially access sensitive files or directories that should be protected. This vulnerability can be particularly dangerous in environments where directory listings might contain sensitive information such as configuration files, backup copies, or other resources that should remain hidden from unauthorized users. The ability to bypass index page restrictions means that attackers can navigate through directory structures without proper authentication, potentially leading to further exploitation opportunities. This vulnerability aligns with CWE-200, which addresses improper output neutralization for logs, and represents a classic example of information exposure through improper access control. The attack vector requires minimal sophistication and can be executed through simple URL manipulation, making it particularly concerning for widespread exploitation.
Organizations affected by this vulnerability should implement immediate mitigations including disabling the Multiviews feature when it is not required for specific applications, updating to patched versions of Apache 1.3.20, and implementing proper access controls for directory structures. The recommended approach involves modifying the Apache configuration to disable Multiviews functionality using the Options directive or by removing the Multiviews option from directory configurations. Additionally, organizations should conduct comprehensive audits of their Apache configurations to identify and remediate similar vulnerabilities across their infrastructure. This vulnerability demonstrates the importance of proper input validation and access control implementation in web server configurations, and aligns with ATT&CK technique T1213 for data from information repositories, as attackers can leverage this vulnerability to harvest directory listings and sensitive information. The vulnerability also relates to T1083 for file and directory discovery, as it provides an automated method for attackers to enumerate directory structures without direct access to the server filesystem.