CVE-2000-0610 in DMailWeb
Summary
by MITRE
NetWin dMailWeb and cwMail 2.6g and earlier allows remote attackers to bypass authentication and use the server for mail relay via a username that contains a carriage return.
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Analysis
by VulDB Data Team • 04/06/2019
The vulnerability identified as CVE-2000-0610 represents a critical authentication bypass flaw affecting NetWin dMailWeb and cwMail versions 2.6g and earlier. This issue stems from inadequate input validation within the authentication mechanism, specifically when processing username credentials containing carriage return characters. The flaw allows remote attackers to manipulate the authentication flow by injecting carriage return sequences into the username field, effectively circumventing the intended security controls.
The technical implementation of this vulnerability exploits a fundamental weakness in how the mail server processes user authentication requests. When a username containing a carriage return character is submitted, the server fails to properly sanitize or validate the input before processing the authentication attempt. This improper handling creates a condition where the server interprets the carriage return as a command delimiter, potentially allowing an attacker to inject additional commands or manipulate the authentication sequence. The vulnerability resides in the server's failure to implement proper input sanitization and validation mechanisms, which is classified under CWE-20 as "Improper Input Validation" and aligns with CWE-312 as "Sensitive Data Exposure" when considering the authentication bypass aspect.
The operational impact of this vulnerability is severe as it provides attackers with unauthorized access to the mail server's relay functionality. Once authenticated, an attacker can leverage the server to send emails through the compromised system, potentially using it for spam distribution, phishing campaigns, or as a stepping stone for further network infiltration. This relay capability enables attackers to mask their true IP addresses while conducting malicious activities, making attribution and tracking significantly more difficult. The vulnerability also poses risks to the server's integrity and availability, as unauthorized users can potentially consume server resources through excessive relay attempts.
From a threat modeling perspective, this vulnerability aligns with several ATT&CK tactics including T1566 for "Phishing" and T1190 for "Exploit Public-Facing Application" as attackers can exploit the vulnerable mail server to send phishing emails or conduct other malicious activities. The attack vector requires minimal technical expertise, making it particularly dangerous as it can be exploited by attackers with basic knowledge of web application vulnerabilities. The vulnerability also demonstrates poor security practices in input handling, which is consistent with ATT&CK technique T1071.004 for "Application Layer Protocol: Email Protocols" where improper handling of email server communications creates exploitable conditions.
Mitigation strategies should focus on immediate patching of affected versions, implementing proper input validation and sanitization for all user-supplied data, and configuring the mail server to reject or properly handle special characters in authentication credentials. Organizations should also implement network-level controls such as firewall rules to restrict access to mail server functionality and monitor for suspicious relay activity. The fix requires modifying the server's authentication routine to properly escape or reject carriage return characters in username fields, ensuring that all input is validated against a strict whitelist of acceptable characters. Additionally, implementing proper logging and monitoring of authentication attempts can help detect exploitation attempts and provide forensic evidence for incident response activities.