CVE-2006-0896 in Simple Machines
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Sources/Register.php in Simple Machine Forum (SMF) 1.0.6 allows remote attackers to inject arbitrary web script or HTML via the X-Forwarded-For HTTP header field.
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Analysis
by VulDB Data Team • 07/19/2018
The vulnerability identified as CVE-2006-0896 represents a critical cross-site scripting flaw within Simple Machine Forum version 1.0.6, specifically affecting the Sources/Register.php component. This vulnerability arises from the forum's improper handling of the X-Forwarded-For HTTP header field during user registration processes, creating an avenue for remote attackers to execute malicious scripts within the context of other users' browsers. The X-Forwarded-For header is commonly used by web applications to identify the originating IP address of a client connecting through a proxy server, making it a legitimate header that applications typically process. However, in this case, SMF fails to properly sanitize or escape the data contained within this header before incorporating it into dynamic web content, leading to potential code injection attacks.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious payload within the X-Forwarded-For header field and submits it through a registration request. When the forum processes this request and displays the header information in the user interface or logs, the embedded script executes in the browser context of any user who views the affected content. This type of vulnerability falls under the CWE-79 category, which specifically addresses Cross-Site Scripting flaws in software applications. The attack vector is particularly concerning because it leverages a standard HTTP header that is commonly passed through proxy servers and load balancers, making it difficult to detect and prevent through conventional security measures. The vulnerability demonstrates a classic improper input validation issue where the application fails to properly escape or filter user-controllable data before rendering it in web pages.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, and data manipulation. An attacker could inject scripts that steal cookies, redirect users to malicious sites, or even modify forum content to spread additional malware. The vulnerability affects the entire user registration process and potentially exposes all users who interact with content that displays the X-Forwarded-For header information. Given that SMF was widely used for community forums and discussion platforms, the potential for widespread impact was significant, as attackers could compromise entire forum installations and user bases. The vulnerability also represents a failure in the principle of least privilege and proper input sanitization, as the application should have treated all HTTP headers as potentially malicious input requiring appropriate validation and escaping.
Mitigation strategies for this vulnerability should include immediate patching of the SMF application to version 1.0.7 or later, which contains the necessary fixes for this XSS vulnerability. Administrators should implement proper input validation and output escaping mechanisms for all HTTP headers, particularly those that are not directly user-controlled but may contain user-supplied data. The implementation of Content Security Policy headers can provide additional protection against script execution, while proper header sanitization should be enforced at the application level. Security monitoring should include detection of unusual patterns in HTTP headers, and the application should be configured to reject or sanitize any header data that contains potentially dangerous characters or script tags. This vulnerability aligns with ATT&CK technique T1566.001, which covers Phishing with Malicious Attachments, as it enables attackers to craft malicious registration requests that can compromise user sessions and access sensitive information. Organizations should also conduct regular security assessments of their web applications to identify similar input validation flaws and ensure that all user-controllable data is properly sanitized before being rendered in web contexts.