CVE-2018-25350 in userSpice
Summary
by MITRE • 05/23/2026
userSpice 4.3.24 contains a username enumeration vulnerability that allows unauthenticated attackers to discover valid usernames by sending POST requests to the existingUsernameCheck.php endpoint. Attackers can submit usernames and analyze response text for the 'taken' string to identify existing accounts in the system.
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Analysis
by VulDB Data Team • 05/25/2026
The username enumeration vulnerability in userSpice 4.3.24 represents a critical security weakness that exposes the system to unauthorized account discovery attempts. This flaw exists within the existingUsernameCheck.php endpoint which lacks proper authentication requirements and response sanitization mechanisms. Attackers can exploit this vulnerability by submitting various usernames through POST requests and analyzing the textual responses for the specific 'taken' string indicator that confirms the existence of valid accounts within the system database.
The technical implementation of this vulnerability stems from inadequate input validation and response handling within the username verification process. When an unauthenticated user submits a username to the existingUsernameCheck.php endpoint, the system responds with distinct text messages that clearly indicate whether the submitted username exists in the database. This predictable response pattern provides attackers with a straightforward method for enumerating valid accounts without requiring any prior authentication credentials or privileged access. The vulnerability directly maps to CWE-623, which specifically addresses the issue of information exposure through improper response handling during authentication processes. The flaw demonstrates poor security design principles where the system's response behavior inadvertently reveals sensitive information about account validity to unauthorized parties.
The operational impact of this vulnerability extends beyond simple account enumeration and creates significant risks for system security and user privacy. An attacker who successfully identifies valid usernames can subsequently target these accounts with brute force attacks, credential stuffing attempts, or social engineering campaigns. The enumeration process allows for automated discovery of user accounts through simple scripting, making it an attractive target for malicious actors seeking to compromise multiple user accounts. This vulnerability also enables attackers to map out the user base of the application, potentially identifying high-value targets or discovering patterns in user naming conventions that could aid further exploitation efforts. The exposure of valid usernames creates a foundation for more sophisticated attacks that could lead to complete system compromise.
Mitigation strategies for this vulnerability should focus on implementing proper authentication requirements for all account verification endpoints and standardizing response handling to prevent information leakage. The existingUsernameCheck.php endpoint must require appropriate authentication checks or implement rate limiting and access controls to prevent unauthorized enumeration attempts. Security measures should include returning consistent responses regardless of whether a username exists, implementing proper input validation to reject malformed requests, and adding additional layers of protection such as CAPTCHA mechanisms or account lockout procedures after multiple failed attempts. Organizations should also consider implementing the principle of least privilege and ensure that all authentication-related endpoints are properly secured against unauthorized access attempts. This vulnerability highlights the importance of following secure coding practices as outlined in the OWASP Top Ten and aligns with ATT&CK technique T1078 which addresses valid accounts and credential access through enumeration and reconnaissance activities.