CVE-2006-2247 in WebCalendar
Summary
by MITRE
WebCalendar 1.0.1 to 1.0.3 generates different error messages depending on whether or not a username is valid, which allows remote attackers to enumerate valid usernames.
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Analysis
by VulDB Data Team • 06/18/2019
The vulnerability identified as CVE-2006-2247 affects WebCalendar versions 1.0.1 through 1.0.3 and represents a classic information disclosure flaw that enables remote attackers to perform user enumeration attacks. This vulnerability stems from the application's inconsistent error handling behavior when processing authentication requests, specifically how it responds to login attempts with different username inputs. The flaw manifests when the system generates distinct error messages based on whether the provided username exists in the system's user database, creating a side-channel attack vector that exposes user account information.
This vulnerability directly maps to CWE-200, which describes the improper exposure of sensitive information, and specifically relates to CWE-384, which addresses session management flaws that can lead to user enumeration. The technical implementation flaw lies in the application's authentication routine where it does not normalize error responses regardless of whether a username is valid or invalid. When an attacker submits a login request with a known username, the system returns one error message, while submitting a request with a non-existent username produces a different error message, creating a clear distinction that attackers can exploit to determine which usernames are legitimate within the system.
The operational impact of this vulnerability extends beyond simple user enumeration, as it provides attackers with foundational information for subsequent attack phases. Once valid usernames are identified, attackers can proceed with brute force attacks, credential stuffing, or social engineering campaigns targeting specific accounts. The vulnerability affects authentication security controls by weakening the system's ability to maintain confidentiality of user account information, potentially enabling privilege escalation attacks or facilitating account takeover attempts. This type of information disclosure can be particularly damaging in environments where user accounts represent legitimate business users or administrative privileges.
The attack surface for this vulnerability is primarily through the web application's login interface, where attackers can systematically test usernames against the authentication system. The attacker's methodology involves sending multiple authentication requests with different username inputs while monitoring the responses to distinguish between valid and invalid accounts based on the differing error messages. Mitigation strategies include implementing consistent error handling that returns identical error messages regardless of whether the username exists, normalizing authentication responses, and implementing account lockout mechanisms or rate limiting to prevent automated enumeration attempts. Organizations should also consider implementing multi-factor authentication and monitoring for unusual authentication patterns to detect potential enumeration attacks. This vulnerability demonstrates the importance of applying the principle of least information disclosure in security design, ensuring that error responses do not reveal sensitive system information that could aid attackers in their reconnaissance activities. The flaw also highlights the necessity of following secure coding practices that prevent side-channel information leakage, as outlined in various security frameworks including the OWASP Top Ten and NIST cybersecurity guidelines.