CVE-2007-0398 in a-forum
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in forum.php3 in Arnaud Guyonne (aka Arnotic) a-forum allow remote attackers to inject arbitrary web script or HTML via the (1) Sujet or (2) Pseudo field.
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Analysis
by VulDB Data Team • 10/06/2017
The vulnerability described in CVE-2007-0398 represents a critical cross-site scripting flaw affecting the a-forum software developed by Arnaud Guyonne. This particular implementation of the vulnerability exists within the forum.php3 script, which serves as the primary interface for user interactions and content posting within the forum application. The flaw specifically targets two user input fields named Sujet and Pseudo, which are commonly used for subject lines and user nicknames respectively in forum environments. The vulnerability was identified in a version of the software that predates modern security standards and robust input sanitization practices, making it particularly susceptible to exploitation by malicious actors.
The technical implementation of this XSS vulnerability stems from inadequate input validation and output encoding within the forum.php3 script. When users submit content through the Sujet and Pseudo fields, the application fails to properly sanitize or escape the input data before rendering it back to other users browsing the forum. This omission creates a direct pathway for attackers to inject malicious JavaScript code or HTML content that executes in the context of other users' browsers. The vulnerability classifies under CWE-79 as "Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')", which is one of the most prevalent and dangerous web application security flaws. The attack vector requires no authentication and can be executed through simple web requests, making it highly exploitable in environments where users trust the forum content.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it can enable sophisticated attack chains within the forum environment. An attacker could inject malicious scripts that steal session cookies, redirect users to phishing sites, or even execute arbitrary commands on affected systems if the forum environment has additional vulnerabilities. The reflected nature of this XSS attack means that the malicious payload is immediately executed in the victim's browser without requiring any server-side storage, making detection and mitigation more challenging. This vulnerability particularly affects community forums where users regularly interact with content posted by others, creating numerous potential attack surfaces. The vulnerability aligns with ATT&CK technique T1566.001 for "Phishing: Spearphishing Attachment" and T1531 for "Account Access Removal" as attackers can leverage the XSS to establish persistent access through session hijacking or credential theft.
Mitigation strategies for this vulnerability require immediate implementation of proper input sanitization and output encoding practices. The most effective solution involves implementing strict input validation that removes or encodes dangerous characters from user submissions before they are processed or stored. The application should employ context-specific output encoding, particularly HTML entity encoding, when rendering user-provided content back to web browsers. Additionally, implementing a Content Security Policy (CSP) header would provide an additional layer of protection against script injection attacks by restricting the sources from which scripts can be loaded. Organizations should also consider implementing proper web application firewalls and regular security scanning to detect similar vulnerabilities. The remediation process should include thorough code review and input validation testing, with a focus on ensuring all user-supplied data is properly escaped or validated before any processing occurs. This vulnerability serves as a classic example of why defense-in-depth security measures are essential, as a single input validation failure can compromise entire user bases within web applications.