CVE-2015-8973 in MyBB
Summary
by MITRE
xmlhttp.php in MyBB (aka MyBulletinBoard) before 1.6.18 and 1.8.x before 1.8.6 and MyBB Merge System before 1.8.6 allows remote attackers to bypass intended access restrictions via vectors related to the forum password.
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Analysis
by VulDB Data Team • 08/08/2020
The vulnerability identified as CVE-2015-8973 affects MyBB bulletin board systems and the MyBB Merge System, specifically targeting versions prior to 1.6.18 and 1.8.x before 1.8.6. This security flaw resides in the xmlhttp.php component which handles asynchronous communication within the forum platform. The vulnerability represents a critical access control bypass that allows remote attackers to circumvent intended security measures protecting forum content through improper handling of forum password validation mechanisms. The flaw enables unauthorized access to protected forum areas that should only be accessible to users who possess the correct forum password, effectively undermining the authentication and authorization controls implemented by the system.
The technical implementation of this vulnerability stems from insufficient validation of forum password credentials within the xmlhttp.php script. When users attempt to access password-protected forums, the system should verify the provided password against the stored credentials before granting access to restricted content. However, the flawed implementation fails to properly authenticate the password check, allowing attackers to bypass these security controls through crafted requests that exploit the weakness in the access validation logic. This issue falls under the CWE-285 access control vulnerability category, specifically related to improper authorization where the system fails to properly enforce access restrictions. The vulnerability demonstrates a classic case of insufficient input validation and authentication checks that can be exploited remotely without requiring any prior authentication credentials or privileged access to the system.
The operational impact of this vulnerability is significant as it allows remote attackers to gain unauthorized access to protected forum content, including private discussions, member directories, and other restricted areas that should only be accessible to legitimate forum members who know the correct forum password. This unauthorized access can lead to data exposure, privacy violations, and potential compromise of user information stored within the forum system. Attackers can exploit this vulnerability to view sensitive content, potentially including personal information of forum members, private messages, and other confidential data that should remain protected. The remote nature of the attack means that threat actors can exploit this vulnerability from anywhere on the internet without requiring physical access to the system or network. This vulnerability directly aligns with ATT&CK technique T1078 which covers legitimate credentials usage and privilege escalation through unauthorized access to protected resources.
Mitigation strategies for this vulnerability require immediate patching of affected MyBB installations to versions 1.6.18 or later for the 1.6.x branch, and 1.8.6 or later for the 1.8.x branch. System administrators should also implement additional security measures including network-level access controls, monitoring for unusual access patterns, and regular security audits of forum configurations. The patch addresses the core issue by implementing proper authentication validation within the xmlhttp.php script, ensuring that forum password checks are properly enforced before granting access to restricted content. Organizations should also consider implementing web application firewalls to detect and block suspicious requests that attempt to exploit this vulnerability, and conduct regular vulnerability assessments to identify similar access control issues within their web applications. Additionally, implementing proper logging and monitoring of access attempts can help detect exploitation attempts and provide evidence for forensic analysis. The vulnerability serves as a reminder of the critical importance of proper access control implementation in web applications and the need for regular security updates to address known vulnerabilities in open source software platforms.