CVE-2006-0155 in Fourtwosevenbb
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in posts.php in 427BB 2.2 and 2.2.1 allows remote attackers to inject arbitrary Javascript via a new message with a url bbcode tag containing a javascript URI.
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Analysis
by VulDB Data Team • 01/11/2019
The vulnerability described in CVE-2006-0155 represents a classic cross-site scripting flaw within the 427BB 2.2 and 2.2.1 bulletin board software, classified under CWE-79 as "Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')". This security weakness specifically manifests in the posts.php script which processes user-generated content and fails to properly sanitize or escape input data before rendering it in web pages. The vulnerability occurs when users submit new messages containing URL bbcode tags that include javascript URIs, allowing malicious actors to inject executable javascript code into the forum's output.
The technical exploitation of this vulnerability relies on the software's insufficient validation of user input within the bbcode processing functionality. When a user creates a post with a malicious url bbcode tag containing javascript code, the application does not adequately filter or escape the content before storing or displaying it to other forum users. This creates a persistent XSS vector where the injected javascript executes in the context of other users' browsers when they view the affected posts. The vulnerability is particularly dangerous because it operates at the application layer, targeting the web interface rather than network protocols or system-level components.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it enables attackers to perform session hijacking, steal cookies, redirect users to malicious sites, or even execute arbitrary commands on affected systems. Since the vulnerability affects the core posting functionality of the bulletin board, it can be exploited across all forum threads and posts, potentially compromising thousands of users. The persistence of the attack vector means that once a malicious post is created, it continues to affect users until the post is removed or the vulnerability is patched, creating a significant risk for forum administrators who may not immediately detect such attacks.
Security mitigations for this vulnerability should focus on implementing comprehensive input validation and output encoding mechanisms. The primary defense involves sanitizing all user input before processing, particularly within bbcode and similar markup parsing functions. This includes implementing strict validation of URL formats, escaping special characters in javascript URIs, and employing context-specific output encoding for web content. Organizations should also consider implementing content security policies to prevent execution of unauthorized scripts, and deploy web application firewalls to detect and block suspicious input patterns. The vulnerability aligns with ATT&CK technique T1566.001 for "Phishing with Social Engineering" and T1059.007 for "Command and Scripting Interpreter: JavaScript", demonstrating how this flaw can serve as a launchpad for more sophisticated attacks. Regular security audits of web applications, particularly those handling user-generated content, are essential to identify and remediate similar input validation weaknesses before they can be exploited by threat actors.