CVE-2023-40764 in Car Rental Script
Summary
by MITRE • 08/28/2023
User enumeration is found in PHP Jabbers Car Rental Script v3.0. 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 • 01/28/2026
The vulnerability identified as CVE-2023-40764 represents a critical user enumeration flaw within the PHP Jabbers Car Rental Script version 3.0 that significantly undermines the system's authentication security posture. This weakness manifests specifically during the password recovery process, where the application exhibits inconsistent error messaging that inadvertently reveals whether a given username exists within the system. The vulnerability stems from the application's failure to implement consistent error responses regardless of whether the attempted username is valid or invalid, creating a clear information disclosure channel that adversaries can exploit to identify legitimate user accounts.
From a technical perspective, this vulnerability maps directly to CWE-204, which categorizes information exposure through inconsistent error messages, and represents a classic example of how poor input validation and error handling can create security weaknesses. The flaw operates by analyzing the response time differences and message variations that occur when the system processes password recovery requests for different user accounts. When an attacker submits a password recovery request for a valid user account, the system generates one type of response, whereas submitting the same request for a non-existent account produces a different response, allowing the attacker to distinguish between valid and invalid usernames through careful observation of these discrepancies.
The operational impact of this vulnerability extends far beyond simple information disclosure, as it enables sophisticated brute force attacks and account takeover attempts. Attackers can systematically enumerate valid user accounts by submitting numerous password recovery requests and observing the response patterns, effectively building a list of legitimate usernames that can then be targeted with more focused credential stuffing or brute force attacks. This enumeration capability significantly reduces the complexity of subsequent attacks, as attackers no longer need to guess valid usernames through social engineering or other means. The vulnerability essentially provides an automated account discovery mechanism that undermines the fundamental security principle of keeping user accounts confidential and hidden from unauthorized parties.
The threat landscape surrounding this vulnerability aligns with ATT&CK technique T1078.004, which describes valid accounts as a means of gaining access to systems, particularly when attackers can leverage information about legitimate user accounts to conduct more effective attacks. Organizations using the PHP Jabbers Car Rental Script are particularly vulnerable to this attack vector as the enumeration process can be automated through simple scripts that systematically test username validity, making it an attractive target for both automated attacks and determined adversaries. The vulnerability's impact is exacerbated by the fact that password recovery mechanisms are often designed to be accessible to all users, creating an attack surface that may not be properly secured against malicious enumeration attempts.
Mitigation strategies for CVE-2023-40764 should focus on implementing consistent error handling throughout the password recovery process, ensuring that all user enumeration attempts generate identical responses regardless of account validity. The recommended approach involves standardizing error messages to provide no information about the existence or non-existence of user accounts, implementing rate limiting to prevent automated enumeration attempts, and potentially incorporating CAPTCHA mechanisms to further complicate automated attacks. Additionally, organizations should consider implementing account lockout mechanisms after a certain number of failed recovery attempts, though these must be carefully configured to avoid creating denial-of-service conditions. The fix should also include proper logging and monitoring of password recovery attempts to detect potential enumeration activities and alert security personnel to suspicious behavior patterns that may indicate active exploitation attempts.