CVE-2011-4317 in E-Business Suite
Summary
by MITRE
The mod_proxy module in the Apache HTTP Server 1.3.x through 1.3.42, 2.0.x through 2.0.64, and 2.2.x through 2.2.21, when the Revision 1179239 patch is in place, does not properly interact with use of (1) RewriteRule and (2) ProxyPassMatch pattern matches for configuration of a reverse proxy, which allows remote attackers to send requests to intranet servers via a malformed URI containing an @ (at sign) character and a : (colon) character in invalid positions. NOTE: this vulnerability exists because of an incomplete fix for CVE-2011-3368.
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Analysis
by VulDB Data Team • 09/10/2024
The vulnerability described in CVE-2011-4317 represents a critical flaw in the Apache HTTP Server's mod_proxy module that stems from an incomplete remediation of a previous security issue. This vulnerability affects multiple versions of Apache HTTP Server including the 1.3.x series up to 1.3.42, 2.0.x series up to 2.0.64, and 2.2.x series up to 2.2.21. The flaw specifically manifests when the server employs both RewriteRule directives and ProxyPassMatch pattern matching configurations for reverse proxy functionality, creating a dangerous interaction that can be exploited by remote attackers to bypass intended security controls.
The technical implementation of this vulnerability exploits the improper handling of URI parsing within the mod_proxy module when it encounters malformed URIs containing both @ and : characters in invalid positions. When an attacker crafts a malicious request with these specific character sequences, the server's proxy handling logic fails to properly validate the URI structure, allowing it to process requests that should have been rejected or properly sanitized. This occurs because the patch for CVE-2011-3368, which was intended to address similar issues, was incomplete and did not fully resolve the underlying parsing logic problems. The vulnerability specifically leverages the interaction between URL parsing and proxy configuration patterns, where the server's internal state management becomes compromised when processing these particular character combinations.
The operational impact of this vulnerability is severe and directly enables unauthorized access to internal network resources that should remain protected behind the Apache server's proxy configuration. Attackers can exploit this flaw to send requests to intranet servers that would normally be inaccessible from the internet, effectively bypassing the intended security boundaries of the reverse proxy setup. This creates a significant risk for organizations that rely on Apache servers for external access while maintaining internal services, as the vulnerability allows for potential reconnaissance, data exfiltration, and further exploitation of internal systems. The attack vector is particularly dangerous because it requires minimal privileges and can be executed through standard HTTP requests, making it difficult to detect and prevent through conventional network monitoring approaches.
Organizations affected by this vulnerability should immediately implement comprehensive mitigation strategies focusing on both immediate patching and configuration hardening. The primary remediation involves upgrading to Apache HTTP Server versions that contain complete fixes for both CVE-2011-3368 and CVE-2011-4317, ensuring that all proxy configurations are reviewed and validated against known attack patterns. Security teams should also implement additional monitoring for suspicious URI patterns containing malformed @ and : character sequences, while considering the application of web application firewalls to detect and block such malicious requests. The vulnerability aligns with ATT&CK technique T1071.004 for application layer protocol manipulation and CWE-20 for improper input validation, highlighting the importance of robust input sanitization and proper state management in proxy server implementations. Additionally, organizations should conduct thorough security assessments of their existing proxy configurations to identify any other potential interaction patterns that might create similar vulnerabilities in their infrastructure.