CVE-2006-3796 in DeluxeBB
Summary
by MITRE
DeluxeBB 1.07 and earlier does not properly handle a username composed of a single space character, which allows remote authenticated users to login as the "space" user, post as the guest user, and block the ability of an administrator to ban the "space" user.
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Analysis
by VulDB Data Team • 07/31/2018
This vulnerability exists in DeluxeBB version 1.07 and earlier, representing a critical authentication and privilege escalation flaw that undermines the forum's user management system. The issue stems from the application's improper validation of username inputs, specifically failing to reject or properly sanitize usernames consisting of a single space character. This fundamental flaw in input handling creates a security loophole that allows authenticated users to exploit the system's user account management mechanisms.
The technical implementation of this vulnerability demonstrates a classic case of inadequate input sanitization and validation, which falls under CWE-20 - Improper Input Validation. When a user creates an account or logs in with a username containing only a space character, the system processes this input without proper validation, effectively creating a legitimate user account that can be used to bypass normal access controls. This flaw operates at the application logic level, where the authentication routine fails to distinguish between valid and invalid username formats, allowing malicious users to create accounts with whitespace-only usernames.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it enables attackers to manipulate the forum's user database in ways that can severely disrupt normal operations. An attacker can log in as the "space" user account, which then allows them to post messages as the guest user, effectively bypassing the normal user authentication system. This creates a persistent threat where the malicious user can make posts, potentially spreading spam or malicious content while remaining anonymous to other users. Furthermore, the vulnerability prevents administrators from properly banning this user account, creating a persistent backdoor that can be exploited repeatedly.
The security implications of this vulnerability align with several ATT&CK techniques including T1078 - Valid Accounts and T1566 - Phishing, as it allows for unauthorized access through legitimate account creation and manipulation. The flaw also represents a privilege escalation vector since it enables users to effectively impersonate other users or gain elevated privileges through the creation of malicious accounts. Additionally, this vulnerability demonstrates poor access control implementation, which can be categorized under ATT&CK technique T1484 - Domain Policy Modification when considering the broader impact on user management and access control policies.
Mitigation strategies should focus on implementing robust input validation at multiple levels within the application. The system must validate all username inputs to reject whitespace-only strings and enforce minimum length requirements for user accounts. This includes implementing server-side validation that checks for empty strings, whitespace-only inputs, and other malformed username patterns before creating or accepting user accounts. Security patches should include proper sanitization of user inputs to remove or reject special characters that could be used to exploit similar vulnerabilities. Administrators should also implement regular monitoring of user accounts to detect and remove any suspicious accounts that may have been created through this vulnerability. The fix should be implemented as a comprehensive input validation routine that prevents the creation of accounts with invalid username formats, ensuring that the system maintains proper user identification and access control mechanisms.