CVE-2006-1089 in PunBB
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in header.php in PunBB 1.2.10 allows remote attackers to inject arbitrary web script or HTML via the URL, which is not properly handled when the PHP_SELF variable is used to handle a pun_page tag.
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Analysis
by VulDB Data Team • 07/20/2018
The vulnerability described in CVE-2006-1089 represents a classic cross-site scripting flaw that existed within the PunBB 1.2.10 bulletin board system. This issue arises from inadequate input validation and sanitization within the header.php file, specifically when processing the PHP_SELF variable during pun_page tag handling. The flaw demonstrates a fundamental weakness in how the application processes and renders user-supplied URL parameters, creating an avenue for malicious actors to execute arbitrary web scripts in the context of other users' browsers. The vulnerability is particularly concerning as it affects the core header functionality of the forum system, potentially allowing attackers to compromise user sessions and execute malicious code across multiple forum pages.
The technical implementation of this vulnerability stems from the improper handling of the PHP_SELF server variable, which contains the filename of the currently executing script. When PunBB processes the pun_page tag, it fails to adequately sanitize or escape the URL parameters that are passed through the PHP_SELF variable, creating a direct injection point for malicious payloads. This type of flaw aligns with CWE-79, which specifically addresses cross-site scripting vulnerabilities resulting from insufficient input validation and output encoding. The vulnerability operates at the application layer and can be exploited through a simple URL manipulation attack, making it particularly dangerous as it requires minimal technical expertise to execute successfully.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform session hijacking, steal user credentials, and manipulate forum content. When a user visits a maliciously crafted URL that triggers this vulnerability, the injected scripts execute within the victim's browser context, potentially allowing attackers to access private forum data, post malicious content, or redirect users to phishing sites. The attack vector is particularly insidious because it leverages the legitimate PHP_SELF variable usage, making the malicious code appear to originate from a trusted source within the forum application. This vulnerability can also facilitate more sophisticated attacks such as credential theft or data exfiltration through the exploitation of the user's authenticated session.
Mitigation strategies for CVE-2006-1089 should focus on implementing proper input validation and output sanitization techniques throughout the PunBB application. The most effective immediate fix involves sanitizing all URL parameters and user inputs before they are processed by the PHP_SELF variable, ensuring that special characters are properly escaped or encoded. Organizations should implement comprehensive input validation that filters out potentially malicious content and apply output encoding to all dynamic content rendered in web pages. The solution should align with ATT&CK technique T1190, which covers the exploitation of vulnerabilities in web applications through cross-site scripting attacks. Additionally, the application should be updated to a patched version of PunBB that addresses this specific vulnerability, as the original version contains multiple other security weaknesses that compound the risk. Regular security audits and input validation testing should be implemented to prevent similar vulnerabilities from emerging in future versions of the forum software.