CVE-2011-5133 in MyBB
Summary
by MITRE
Unspecified vulnerability in MyBB before 1.6.5 has unknown impact and attack vectors, related to an "unparsed user avatar in the buddy list."
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Analysis
by VulDB Data Team • 02/20/2019
The vulnerability identified as CVE-2011-5133 affects MyBB versions prior to 1.6.5 and involves a security flaw related to user avatar handling within the buddy list functionality. This unspecified vulnerability presents a significant concern as it relates to how user-generated content is processed and displayed within the forum software's user interface. The issue specifically manifests when user avatars are rendered in the buddy list context, suggesting that the parsing or sanitization mechanisms for avatar data may be insufficient to prevent malicious input from being executed or displayed inappropriately. The lack of specific details regarding the exact nature of the vulnerability in the initial description indicates that this may have been a complex issue requiring careful analysis to understand the full attack surface and potential exploitation methods.
The technical flaw appears to stem from improper handling of user avatar data within the buddy list feature, which is a core functionality of MyBB's user management system. This type of vulnerability typically falls under CWE-119 Improper Access to Stored Data or CWE-79 Cross-Site Scripting, as user avatar data often contains HTML or JavaScript that should be properly sanitized before display. When avatars are displayed in the buddy list without proper validation or sanitization, malicious users could potentially inject harmful code that executes in the context of other users' browsers. The vulnerability's presence in the buddy list suggests that the application's input validation mechanisms may not adequately distinguish between legitimate and malicious avatar content, particularly when dealing with user-submitted data that can be rendered in multiple contexts within the forum's interface.
The operational impact of this vulnerability extends beyond simple display issues, as it represents a potential vector for cross-site scripting attacks that could compromise user sessions or enable attackers to perform unauthorized actions within the forum environment. When user avatars are improperly handled in the buddy list, malicious actors could exploit this weakness to inject JavaScript code that might steal cookies, redirect users to malicious sites, or perform actions on behalf of other users. The vulnerability's potential for widespread impact is significant since the buddy list is a frequently accessed feature, meaning that any exploited XSS vulnerability could affect a large number of users. This type of vulnerability also aligns with ATT&CK technique T1566.001 Phishing via Social Media, where attackers could use the compromised avatar functionality to deliver malicious payloads to unsuspecting users who view their buddy lists.
The security implications of CVE-2011-5133 highlight the importance of proper input validation and output encoding in web applications, particularly when dealing with user-generated content. The vulnerability demonstrates how seemingly innocuous features like user avatars can become attack vectors when proper security measures are not implemented. Organizations using MyBB versions prior to 1.6.5 should immediately implement security patches to address this issue, as the lack of specific details about the vulnerability's exploitation methods suggests that it may be easily exploitable by attackers with basic knowledge of web security principles. The recommended mitigation involves updating to MyBB 1.6.5 or later versions where the vulnerability has been addressed through proper sanitization of avatar data and enhanced validation mechanisms for user-submitted content. Additionally, administrators should implement proper content security policies and monitor user avatar uploads for suspicious patterns to prevent exploitation of similar vulnerabilities in the future.