CVE-2017-16780 in MyBB
Summary
by MITRE
The installer in MyBB before 1.8.13 allows remote attackers to execute arbitrary code by writing to the configuration file.
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Analysis
by VulDB Data Team • 09/17/2025
The vulnerability identified as CVE-2017-16780 represents a critical remote code execution flaw within the MyBB bulletin board system installer component. This vulnerability affects versions prior to 1.8.13 and stems from improper input validation during the installation process. The core issue arises when the installer fails to properly sanitize user-supplied data before writing configuration parameters to the system's configuration file. This weakness creates an opportunity for remote attackers to inject malicious code or commands that will be executed with the privileges of the web server process. The vulnerability is particularly dangerous because it allows attackers to gain arbitrary code execution capabilities without requiring authentication or prior access to the system. The installer component typically runs with elevated privileges to write configuration files, making this attack vector especially severe as it can potentially lead to full system compromise.
The technical implementation of this vulnerability involves the installer's handling of configuration parameters during the setup process. When attackers can manipulate the installation flow, they can inject malicious content into the configuration file that gets processed by the application. This occurs due to insufficient sanitization of input fields that control various configuration settings. The flaw essentially allows for a form of code injection where attacker-controlled data is written directly to a file that will later be interpreted or executed by the application. This type of vulnerability aligns with CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and is classified as a code injection vulnerability that enables arbitrary code execution. The ATT&CK framework would categorize this under T1059.007 for "Command and Scripting Interpreter: PowerShell" and potentially T1078 for "Valid Accounts" if the web server account has elevated privileges.
The operational impact of this vulnerability extends beyond simple code execution to potentially enable complete system compromise. Attackers can leverage this vulnerability to deploy web shells, modify existing application functionality, steal sensitive data, or establish persistent access to the compromised system. The vulnerability affects the entire installation lifecycle and can be exploited at any point where the installer is accessible to remote users. Given that MyBB is a widely used bulletin board system, this vulnerability could impact numerous websites and organizations that rely on this platform for community forums and discussion boards. The risk is compounded by the fact that many organizations may not immediately patch their systems, especially if they are running older versions of MyBB that are still vulnerable. Additionally, the vulnerability could be exploited in conjunction with other attack vectors to escalate privileges or move laterally within a network, making it a significant concern for organizations with multiple web applications or services.
Mitigation strategies for CVE-2017-16780 focus primarily on immediate patching and access control measures. Organizations should immediately upgrade to MyBB version 1.8.13 or later, which contains the necessary fixes to address the configuration file writing vulnerability. System administrators should also implement network segmentation to limit access to the installer component, ensuring that only authorized personnel can execute installation procedures. Additional protective measures include restricting write permissions on configuration files, implementing proper input validation at all levels, and monitoring system logs for suspicious activity related to configuration file modifications. Security monitoring should specifically look for unusual file modification patterns or attempts to write to sensitive system locations. The vulnerability demonstrates the importance of proper input validation and secure file handling practices, particularly in installation and configuration components that operate with elevated privileges. Organizations should also consider implementing web application firewalls to detect and block malicious attempts to exploit this vulnerability, and conduct regular security assessments to identify similar issues in other applications and systems.