CVE-2006-2908 in MyBB
Summary
by MITRE
The domecode function in inc/functions_post.php in MyBulletinBoard (MyBB) 1.1.2, and possibly other versions, allows remote attackers to execute arbitrary PHP code via the username field, which is used in a preg_replace function call with a /e (executable) modifier.
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Analysis
by VulDB Data Team • 04/30/2019
The vulnerability identified as CVE-2006-2908 represents a critical remote code execution flaw in MyBulletinBoard version 1.1.2 and potentially other iterations within the same release series. This security weakness resides within the domecode function located in the inc/functions_post.php file, which processes user input through a dangerously misconfigured regular expression operation. The vulnerability specifically exploits the use of the /e modifier in a preg_replace function call, creating an avenue for malicious actors to inject and execute arbitrary PHP code on the affected server.
The technical exploitation mechanism leverages the /e flag in preg_replace which, when combined with user-controllable input from the username field, transforms the regular expression evaluation into an executable code execution context. This pattern directly aligns with CWE-94, which classifies the vulnerability as an "Improper Neutralization of Special Elements used in an OS Command" and more specifically maps to CWE-78, "Improper Neutralization of Special Elements used in a Command or Query." The flaw essentially allows attackers to inject PHP code that gets executed during the preg_replace operation, bypassing normal input validation mechanisms and directly compromising the server's execution environment.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise and potential data breaches. An attacker who successfully exploits this vulnerability can execute arbitrary commands with the privileges of the web server process, potentially leading to full system control, data exfiltration, or the installation of backdoors. The vulnerability affects bulletin board systems that rely on user-generated content processing, making it particularly dangerous in environments where multiple users interact with the platform. This weakness can be exploited through various attack vectors including forum posts, user profiles, or any interface element that accepts username input, creating a persistent threat that can be leveraged for extended compromise operations.
Mitigation strategies for CVE-2006-2908 require immediate remediation through software updates to patched versions of MyBulletinBoard, as the vulnerability stems from a fundamental design flaw in the codebase that was addressed in subsequent releases. Organizations should implement input validation measures that prevent special regex characters from being processed in executable contexts, specifically avoiding the use of the /e modifier in preg_replace operations. The remediation process should include comprehensive code audits to identify similar patterns across the application, as this vulnerability type falls under the ATT&CK technique T1059.007 for "Command and Scripting Interpreter: Python" and T1021.004 for "Remote Services: SSH" when considering the broader attack surface. Additionally, implementing web application firewalls and input sanitization layers can provide additional defense-in-depth measures, though these should not replace the core patching requirement. The vulnerability demonstrates the critical importance of avoiding dangerous PHP functions and maintaining secure coding practices throughout the development lifecycle, particularly when handling user-provided data in contexts that could lead to code execution.