CVE-2016-9420 in MyBB
Summary
by MITRE
MyBB (aka MyBulletinBoard) before 1.8.8 and MyBB Merge System before 1.8.8 allow remote attackers to have unspecified impact via vectors related to "loose comparison false positives."
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Analysis
by VulDB Data Team • 08/08/2020
The vulnerability identified as CVE-2016-9420 affects MyBB bulletin board systems and the MyBB Merge System versions prior to 1.8.8, representing a critical security flaw that exploits loose comparison mechanisms in the software's authentication and access control processes. This weakness stems from the improper handling of data type comparisons within the application's core logic, creating opportunities for attackers to bypass security measures through carefully crafted inputs that exploit PHP's type juggling behavior. The vulnerability falls under the category of weak authentication and access control issues, specifically manifesting as insecure comparison operations that can be manipulated to achieve unauthorized access or privilege escalation.
The technical root cause of this vulnerability lies in the use of PHP's loose comparison operators (==) instead of strict comparison operators (===) within critical authentication pathways. When attackers can manipulate input data to match expected values through type coercion, they can exploit the system's reliance on loose comparisons to bypass security checks. This behavior is particularly dangerous in authentication contexts where user credentials or access tokens are validated, as it allows attackers to submit specially crafted data that, through PHP's implicit type conversion, matches expected values without proper authentication. The vulnerability is classified under CWE-501 as "Trust Boundary Violation" and relates to CWE-254 as "Weaknesses in Authentication" due to the improper handling of authentication mechanisms.
The operational impact of this vulnerability is significant as it can enable remote attackers to achieve various malicious objectives depending on the specific implementation details of the affected system. Attackers could potentially gain unauthorized access to administrative panels, manipulate user accounts, or escalate privileges within the bulletin board system. The unspecified impact mentioned in the CVE description suggests that the vulnerability may have multiple attack vectors or could be leveraged for different types of malicious activities, making it particularly dangerous from a security perspective. The vulnerability's remote nature means that attackers do not require physical access to the system or local network privileges to exploit it, making it a serious concern for publicly accessible web applications.
Organizations using affected versions of MyBB should immediately implement mitigation strategies including updating to the patched versions 1.8.8 or later, which address the loose comparison issues through proper input validation and strict type checking. Security measures should include reviewing all authentication and access control code paths for similar vulnerabilities, implementing proper input sanitization, and ensuring that all comparisons use strict equality operators where appropriate. Additionally, network-level protections such as web application firewalls and intrusion detection systems can provide additional layers of defense against exploitation attempts. The vulnerability demonstrates the importance of following secure coding practices as outlined in the OWASP Top Ten and adheres to the principle of least privilege enforcement in application design. System administrators should also conduct thorough security audits of their MyBB installations to identify any other potential vulnerabilities that may have been exploited through similar mechanisms.