CVE-2002-0955 in YaBB
Summary
by MITRE
Cross-site scripting vulnerability in YaBB.cgi for Yet Another Bulletin Board (YaBB) 1 Gold SP1 and earlier allows remote attackers to execute arbitrary script as other web site visitors via script in the num parameter, which is not filtered in the resulting error message.
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Analysis
by VulDB Data Team • 08/30/2024
The vulnerability identified as CVE-2002-0955 represents a critical cross-site scripting flaw within the YaBB bulletin board software version 1 Gold SP1 and earlier releases. This security weakness resides in the YaBB.cgi script which processes user input without proper sanitization, creating an environment where malicious actors can inject arbitrary JavaScript code into web pages viewed by other users. The vulnerability specifically manifests when the num parameter is manipulated in a way that bypasses input validation mechanisms, allowing attackers to embed malicious scripts that execute in the context of other users' browsers.
The technical exploitation of this vulnerability occurs through the manipulation of the num parameter within the YaBB.cgi script, which fails to properly filter or escape user-supplied input before incorporating it into error messages displayed on web pages. This lack of input sanitization creates a classic XSS attack vector where an attacker can craft malicious payloads that get executed when other users browse affected pages. The vulnerability is particularly dangerous because it leverages error handling mechanisms rather than legitimate user input fields, making it more difficult to detect and prevent through standard security measures. According to CWE-79, this represents a classic cross-site scripting weakness where untrusted data is directly embedded into web pages without proper validation or encoding.
The operational impact of CVE-2002-0955 extends beyond simple script execution, as it can enable attackers to steal session cookies, redirect users to malicious websites, deface web pages, or perform actions on behalf of authenticated users. The vulnerability affects all users of the affected YaBB versions, making it a widespread concern for any organization running this bulletin board software. The attack requires minimal privileges and can be executed through simple web browser manipulation, making it particularly dangerous for public forums where many users interact with the system. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, specifically web shell execution, and T1531 for account access through credential theft, as session hijacking becomes possible through cookie theft.
Mitigation strategies for this vulnerability require immediate implementation of input validation and output encoding mechanisms within the YaBB software. Organizations should apply the vendor-provided security patches or upgrade to newer versions of YaBB that address this XSS vulnerability. The solution involves implementing proper input sanitization techniques that filter or escape all user-supplied data before it is processed or displayed in web pages. Security measures should include implementing Content Security Policy headers, using proper HTML encoding for dynamic content, and ensuring all parameters are validated against expected input formats. Additionally, organizations should consider implementing web application firewalls to detect and block malicious input patterns, and establish regular security audits to identify similar vulnerabilities in other web applications. The remediation process should also include user education about the risks of clicking suspicious links and the importance of keeping software updated to prevent exploitation of known vulnerabilities.