Source: cve@mitre.org
member.php in MyBB (aka MyBulletinBoard) before 1.4.12 makes a certain superfluous call to the SQL COUNT function, which allows remote attackers to cause a denial of service (resource consumption) by making requests to member.php that trigger scans of the entire users table.
MyBB versions prior to 1.4.12 are vulnerable to a denial-of-service (DoS) attack. By sending crafted requests to member.php, attackers can trigger excessive database queries, leading to resource exhaustion and making the forum unavailable to legitimate users.
Step 1: Request Initiation: An attacker sends a specially crafted HTTP request to member.php on a vulnerable MyBB forum. The specific parameters in the request are not critical, as the vulnerability is triggered by the mere execution of the script.
Step 2: Script Execution: The member.php script is executed by the web server.
Step 3: Unnecessary COUNT Query: The script, due to the flawed logic, executes a SQL COUNT query against the users table to determine the total number of users.
Step 4: Database Overload: Repeated execution of the COUNT query, especially with a large user base, consumes significant database resources (CPU, I/O).
Step 5: Resource Exhaustion: The database server becomes overloaded, leading to slow response times or complete unavailability.
Step 6: Denial of Service: Legitimate users are unable to access the forum due to the database being overwhelmed, resulting in a DoS condition.
The vulnerability lies in the member.php script's inefficient use of the SQL COUNT function. Before version 1.4.12, the script made a superfluous call to COUNT to determine the total number of users, even when this information wasn't strictly necessary for the requested operation. This query, when triggered repeatedly, places a significant load on the database server, especially on large forums. The root cause is a lack of optimization in the SQL query logic, leading to an unnecessary and computationally expensive operation. This is not a classic vulnerability like a buffer overflow or SQL injection, but rather a performance-related flaw that can be exploited for DoS.
This vulnerability is not typically associated with specific Advanced Persistent Threats (APTs) or known malware campaigns due to its simplicity. However, any attacker seeking to disrupt a MyBB forum could leverage this. CISA KEV status: Not listed.
Monitor database server resource utilization (CPU, I/O, memory). Spikes in resource usage, especially during periods of normal forum activity, could indicate an attack.
Analyze web server logs for a high volume of requests to member.php. Specifically, look for unusual request patterns or repeated requests from the same IP addresses.
Monitor database query logs for excessive execution of SELECT COUNT(*) FROM users queries, especially if they are originating from member.php.
Implement intrusion detection system (IDS) rules to detect suspicious traffic patterns targeting member.php.
Upgrade MyBB to version 1.4.12 or later. This is the primary and most effective remediation.
Implement rate limiting on requests to member.php to mitigate the impact of potential attacks.
Optimize the database server configuration (e.g., increase memory allocation, tune query caching) to handle increased load.
Implement a web application firewall (WAF) to filter malicious requests and protect against DoS attacks.
Monitor server logs and database activity to identify and respond to suspicious behavior.