CVE-2002-1313 in Nullmailer
Summary
by MITRE
nullmailer 1.00RC5 and earlier allows local users to cause a denial of service via an email to a local user that does not exist, which generates an error that causes nullmailer to stop sending mail to all users.
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Analysis
by VulDB Data Team • 05/01/2019
The vulnerability identified as CVE-2002-1313 affects nullmailer version 1.00RC5 and earlier, representing a critical denial of service weakness in mail handling systems. This flaw manifests when the mailer processes an email directed to a non-existent local user account, triggering an error condition that causes the entire mail delivery system to halt operations. The issue stems from inadequate error handling mechanisms within the nullmailer application, which fails to gracefully manage invalid recipient addresses.
The technical implementation of this vulnerability involves the mailer's failure to properly validate recipient addresses before attempting delivery processing. When a message is received for a nonexistent local user, the system generates an unhandled error condition that propagates through the application's execution flow, ultimately resulting in process termination. This error handling deficiency creates a cascading failure where the mailer's inability to continue processing subsequent messages affects all user accounts within the system. The flaw operates at the application level and represents a classic case of improper error handling that violates security best practices.
From an operational impact perspective, this vulnerability creates a severe disruption to mail services by effectively stopping all mail delivery operations when a single invalid recipient is encountered. The denial of service affects all users on the system since the mailer process terminates completely rather than continuing to service other legitimate mail requests. This vulnerability particularly impacts systems where nullmailer serves as the primary mail transfer agent, as it can be exploited by any local user with the ability to send email messages. The attack vector is simple and requires minimal privileges, making it highly exploitable within local network environments.
The vulnerability aligns with CWE-704 in the Common Weakness Enumeration catalog, which classifies improper error handling as a weakness that can lead to system instability and denial of service conditions. From an ATT&CK framework perspective, this weakness maps to T1499.004 which covers network disruption through resource exhaustion or service interruption. The flaw demonstrates a fundamental lack of robust error handling design principles that should be implemented in all mail processing systems. Organizations should consider this vulnerability as part of broader security hardening efforts, particularly in environments where local user privileges are not strictly controlled.
Mitigation strategies for CVE-2002-1313 include upgrading to nullmailer version 1.00RC6 or later, which contains the necessary error handling fixes to prevent process termination upon encountering invalid recipients. System administrators should implement proper input validation mechanisms and ensure that all mail processing applications handle error conditions gracefully without terminating core services. Additionally, implementing monitoring systems to detect unusual mail processing behavior can help identify exploitation attempts. The fix addresses the root cause by ensuring that error conditions do not result in application termination, thereby maintaining service availability for legitimate users. Regular security updates and vulnerability assessments should be conducted to prevent similar issues in other mail handling components within the infrastructure.