CVE-2023-33562 in Time Slots Booking Calendar
Summary
by MITRE • 08/02/2023
User enumeration is found in in PHP Jabbers Time Slots Booking Calendar v3.3. This issue occurs during password recovery, where a difference in messages could allow an attacker to determine if the user is valid or not, enabling a brute force attack with valid users.
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Analysis
by VulDB Data Team • 01/05/2026
The vulnerability identified as CVE-2023-33562 represents a critical user enumeration flaw within the PHP Jabbers Time Slots Booking Calendar version 3.3 system. This weakness manifests during the password recovery process, where the application fails to provide consistent error messaging for all user account attempts. The vulnerability stems from the application's differential response behavior, where valid user accounts generate different error messages compared to invalid ones, creating a predictable pattern that attackers can exploit for reconnaissance purposes. Such a flaw directly violates security best practices by exposing user account status information through subtle behavioral differences in system responses.
The technical implementation of this vulnerability operates through the password recovery mechanism where users input their email addresses to initiate account recovery processes. When an attacker submits an email address that corresponds to a valid user account, the system returns one type of error message indicating that a recovery email has been sent. However, when an attacker inputs an email address that does not correspond to any registered user, the system generates a different message indicating that no account was found. This inconsistency in error handling creates a timing and response difference that can be systematically exploited to enumerate valid user accounts. The vulnerability falls under the Common Weakness Enumeration category CWE-200, which specifically addresses information exposure through improper error handling, and aligns with ATT&CK technique T1087.001 for account discovery through enumeration of valid accounts.
The operational impact of this vulnerability extends beyond simple user enumeration, as it enables sophisticated brute force attacks against the system's authentication mechanisms. Attackers can systematically test email addresses against the password recovery endpoint, using the differential responses to identify valid accounts within the user base. Once valid accounts are identified, attackers can proceed with targeted credential stuffing, password spraying, or more intensive brute force attacks against those specific user accounts. This vulnerability particularly affects organizations that rely on the time slots booking calendar for customer management, as it exposes the underlying user directory to automated enumeration attacks. The risk is amplified when the system lacks proper rate limiting or account lockout mechanisms, which would otherwise provide additional protection against such attacks.
Mitigation strategies for CVE-2023-33562 require immediate implementation of consistent error handling throughout the password recovery process. The system should return identical error messages regardless of whether the submitted email address corresponds to a valid user account, eliminating the differential response that enables enumeration. Organizations should implement rate limiting mechanisms to restrict the number of password recovery requests per user or IP address within a given time period, preventing automated enumeration attempts. Additionally, implementing account lockout mechanisms after a certain number of failed recovery attempts can further deter brute force attacks. The solution should also include logging and monitoring of password recovery attempts to detect suspicious activity patterns. Security teams should ensure that all user-facing error messages are generic and do not provide information about account validity, aligning with security principles outlined in OWASP Top 10 and NIST cybersecurity guidelines. Regular security assessments and code reviews should be conducted to identify similar vulnerabilities in other application components that may expose user account information through inconsistent error handling behaviors.