CVE-2021-27948 in MyBB
Summary
by MITRE • 03/16/2021
SQL Injection vulnerability in MyBB before 1.8.26 via User Groups. (issue 3 of 3).
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Analysis
by VulDB Data Team • 04/01/2021
The vulnerability CVE-2021-27948 represents a critical SQL injection flaw affecting MyBB versions prior to 1.8.26, specifically within the User Groups functionality. This vulnerability resides in the application's handling of user group parameters, creating an exploitable condition that allows remote attackers to execute arbitrary SQL commands against the underlying database. The issue manifests when the application fails to properly sanitize or validate user input related to group membership and permissions, enabling malicious actors to manipulate database queries through crafted inputs. The vulnerability is classified under CWE-89 SQL Injection, which is a fundamental weakness in web applications that directly impacts data integrity and confidentiality. This flaw operates at the application layer, specifically targeting the database interaction mechanisms used by MyBB's user management system.
The technical implementation of this vulnerability occurs when user group parameters are processed without adequate input validation or parameterization. Attackers can exploit this by submitting malicious payloads through user group related functions, potentially manipulating the SQL query structure to extract, modify, or delete database records. The vulnerability is particularly dangerous because it operates within core user management functionality, allowing attackers to escalate privileges, access sensitive user data, or even gain full database control. The exploitation process typically involves crafting SQL injection payloads that bypass input sanitization measures, leveraging the application's trust in user-provided data to inject malicious SQL commands into the execution context. This represents a classic example of improper input handling that violates secure coding principles and creates a direct pathway for database compromise.
The operational impact of CVE-2021-27948 extends beyond simple data theft, as it enables comprehensive database manipulation and potential system compromise. Organizations running affected MyBB versions face risks including unauthorized access to user credentials, personal information disclosure, data corruption, and potential lateral movement within network environments where the application resides. The vulnerability affects the integrity and availability of user group configurations, potentially allowing attackers to grant themselves administrative privileges or disable legitimate user accounts. Given that MyBB is widely used for forum platforms, the impact could be substantial across multiple organizations, especially those with sensitive user data. The vulnerability aligns with ATT&CK technique T1071.004 Application Layer Protocol: DNS, as attackers may use the compromised system to establish command and control channels or exfiltrate data through DNS tunneling methods. The security implications also include potential compliance violations and reputational damage, as the vulnerability could lead to unauthorized access to protected health information or financial data depending on the forum's content and user base.
Mitigation strategies for CVE-2021-27948 focus primarily on immediate version upgrades to MyBB 1.8.26 or later, which contain the necessary patches to address the SQL injection vulnerability. Organizations should implement comprehensive input validation and parameterization for all user group related functions, ensuring that any user-provided data undergoes strict sanitization before database interaction. The implementation of prepared statements and stored procedures can significantly reduce the risk of SQL injection exploitation by separating SQL code from data. Network segmentation and access controls should be enforced to limit exposure of vulnerable components, while regular security audits and penetration testing can help identify similar vulnerabilities in related systems. Additionally, implementing web application firewalls and intrusion detection systems can provide additional layers of protection against exploitation attempts. The vulnerability demonstrates the importance of maintaining up-to-date software versions and implementing robust input validation as core security practices, aligning with industry standards such as NIST SP 800-160 and ISO/IEC 27001 requirements for secure application development and maintenance.