CVE-2006-7013 in Simple Machines
Summary
by MITRE
** DISPUTED ** QueryString.php in Simple Machines Forum (SMF) 1.0.7 and earlier, and 1.1rc2 and earlier, allows remote attackers to more easily spoof the IP address and evade banning via a modified X-Forwarded-For HTTP header, which is preferred instead of other more reliable sources for the IP address. NOTE: the original researcher claims that the vendor has disputed this issue.
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Analysis
by VulDB Data Team • 08/08/2024
The vulnerability described in CVE-2006-7013 pertains to a significant security flaw in Simple Machines Forum software versions 1.0.7 and earlier, as well as 1.1rc2 and earlier releases. This issue specifically targets the QueryString.php component of the forum software, which handles HTTP request processing and IP address determination for user identification and access control purposes. The vulnerability arises from the software's preference for the X-Forwarded-For HTTP header over more reliable IP address sources when determining user locations for access control decisions.
The technical flaw stems from improper input validation and trust assumptions within the SMF codebase. When the forum processes incoming HTTP requests, it relies on the X-Forwarded-For header to identify user IP addresses, particularly for determining whether users should be banned or allowed access to certain forum features. This header is typically added by reverse proxies, load balancers, or other network infrastructure components to preserve the original client IP address when requests pass through multiple servers. However, the SMF implementation fails to properly validate or sanitize this header, allowing malicious actors to manipulate its contents and present false IP addresses to the forum system.
The operational impact of this vulnerability is substantial as it enables remote attackers to bypass IP-based access controls and spam prevention mechanisms that are fundamental to maintaining forum security and integrity. Attackers can exploit this weakness by crafting malicious HTTP requests with modified X-Forwarded-For headers that contain false IP addresses, potentially allowing them to circumvent existing bans, evade rate limiting, and perform malicious activities such as spam posting or forum abuse without detection. This manipulation undermines the effectiveness of IP-based security measures that administrators rely on to maintain their forum's security posture.
From a cybersecurity perspective, this vulnerability aligns with CWE-284 Access Control Issues, specifically concerning improper access control mechanisms that allow unauthorized access to resources. The flaw also relates to ATT&CK technique T1071.004 Application Layer Protocol: DNS, where attackers manipulate HTTP headers to achieve their objectives. The vulnerability demonstrates a classic case of trusting unvalidated user input without proper sanitization or verification processes, which represents a fundamental security principle violation in web application development.
Organizations using affected SMF versions should immediately implement mitigations including disabling the problematic X-Forwarded-For header processing, implementing additional validation mechanisms for IP address determination, and ensuring that access control decisions are based on multiple verified sources rather than relying on a single potentially manipulable header. The vendor's disputed status of this issue does not diminish the practical security implications for affected installations, making proactive mitigation essential. Regular security audits and input validation improvements should be prioritized to prevent similar vulnerabilities in future implementations, particularly when dealing with HTTP headers that can be easily manipulated by remote attackers.