CVE-2012-2687 in HTTP Server
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in the make_variant_list function in mod_negotiation.c in the mod_negotiation module in the Apache HTTP Server 2.4.x before 2.4.3, when the MultiViews option is enabled, allow remote attackers to inject arbitrary web script or HTML via a crafted filename that is not properly handled during construction of a variant list.
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Analysis
by VulDB Data Team • 05/20/2021
The CVE-2012-2687 vulnerability represents a critical cross-site scripting flaw in the Apache HTTP Server's mod_negotiation module that emerged from improper handling of filename variants during content negotiation processes. This vulnerability specifically affects Apache 2.4.x versions prior to 2.4.3 and becomes exploitable when the MultiViews option is enabled in the server configuration. The flaw resides in the make_variant_list function within mod_negotiation.c, which fails to properly sanitize user-supplied input during the construction of variant lists for content negotiation. The vulnerability stems from the server's inability to adequately filter or escape special characters in filenames that are processed through the MultiViews mechanism, creating opportunities for malicious script injection.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious filename containing script code that gets processed by the make_variant_list function. During the content negotiation process, when MultiViews is enabled, Apache attempts to determine the most appropriate content variant based on client preferences and available resources. The vulnerable function does not properly escape or sanitize the filenames before incorporating them into HTML output used for displaying variant lists. This creates a classic XSS vector where attacker-controlled content can be injected into web pages served by the Apache server, potentially allowing execution of malicious scripts in the context of users' browsers.
The operational impact of CVE-2012-2687 extends beyond simple script injection as it can enable sophisticated attack chains that compromise user sessions and data confidentiality. Attackers can leverage this vulnerability to steal cookies, session tokens, or other sensitive information from authenticated users who browse pages containing malicious filenames. The vulnerability also aligns with CWE-79, which specifically addresses cross-site scripting flaws in input validation and output encoding, and can be mapped to ATT&CK technique T1566.001 for initial access through malicious web content. The attack surface is particularly concerning because it can be exploited without requiring authentication or specific user interaction beyond visiting a maliciously crafted URL, making it a significant threat to web application security.
Organizations affected by this vulnerability should prioritize immediate patching of their Apache installations to version 2.4.3 or later, which contains the necessary fixes for proper input sanitization in the mod_negotiation module. Additionally, administrators should consider disabling the MultiViews option in their Apache configurations if the functionality is not required for their specific use cases, as this would eliminate the attack vector entirely. Security monitoring should include detection of suspicious filename patterns in web server logs that might indicate exploitation attempts, particularly those containing script tags or encoded characters. The vulnerability demonstrates the importance of proper input validation and output encoding in web server components, aligning with security best practices outlined in OWASP Top 10 and NIST SP 800-53 security controls for input validation and output encoding.