CVE-2006-4544 in ExBB
Summary
by MITRE
Multiple PHP remote file inclusion vulnerabilities in ExBB 1.9.1, when register_globals is enabled, allow remote attackers to execute arbitrary PHP code via a URL in the exbb[home_path] parameter in files in the modules directory including (1) birstday/birst.php (2) birstday/select.php, (3) birstday/profile_show.php, (4) newusergreatings/pm_newreg.php, (5) punish/p_error.php, (6) punish/profile.php, and (7) threadstop/threadstop.php. NOTE: the (8) modules/userstop/userstop.php vector might overlap CVE-2006-4488, although it is for a slightly different product from the same vendor.
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Analysis
by VulDB Data Team • 08/03/2018
The vulnerability described in CVE-2006-4544 represents a critical remote file inclusion flaw affecting ExBB 1.9.1 bulletin board software when the PHP register_globals directive is enabled. This vulnerability falls under the CWE-88 category of Improper Neutralization of Argument Delimiters in a Command, specifically manifesting as a remote file inclusion attack vector that allows malicious actors to execute arbitrary PHP code on the target system. The flaw exists in multiple files within the modules directory, including birthday and user management modules, creating multiple entry points for exploitation. The vulnerability's severity is amplified by the requirement for register_globals to be enabled, which was a common configuration in older PHP environments and significantly increased the attack surface.
The technical implementation of this vulnerability exploits the insecure handling of user input through the exbb[home_path] parameter, which is processed without proper validation or sanitization. When register_globals is enabled, PHP automatically creates global variables from GET, POST, and cookie data, making it possible for attackers to inject malicious URLs directly into the application's parameter processing. The affected files demonstrate a consistent pattern where the application includes external resources using user-supplied paths, without adequate input validation or access control measures. This creates a scenario where an attacker can craft a malicious URL that gets executed as PHP code when the vulnerable include statement processes the exbb[home_path] parameter.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with complete control over the affected web server. Successful exploitation allows for arbitrary code execution, which can lead to data theft, service disruption, system compromise, and potential lateral movement within the network. The vulnerability affects multiple modules including user registration, profile management, and administrative functions, making it particularly dangerous as it could be used to manipulate user data, bypass authentication mechanisms, or escalate privileges. The overlap with CVE-2006-4488 in the userstop module suggests a broader pattern of insecure parameter handling across the ExBB product line, indicating that similar vulnerabilities may exist in other components of the software suite.
Mitigation strategies for this vulnerability require immediate action to disable the register_globals directive in PHP configurations, as this removes one of the primary prerequisites for exploitation. Organizations should implement proper input validation and sanitization measures, ensuring that all user-supplied parameters are validated against expected formats and ranges before processing. The recommended approach includes implementing whitelisting mechanisms for file inclusion paths and employing secure coding practices that prevent dynamic include statements from accepting user input. Additionally, network segmentation and access control measures should be implemented to limit exposure of vulnerable applications, while regular security audits and vulnerability assessments should be conducted to identify similar issues in other legacy applications. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter and T1190 for exploit public-facing application, highlighting the need for comprehensive application security controls and regular patch management procedures.