CVE-2006-2346 in vpopmail
Summary
by MITRE
vpopmail 5.4.14 and 5.4.15, with cleartext passwords enabled, allows remote attackers to authenticate to an account that does not have a cleartext password set by using a blank password to (1) SMTP AUTH or (2) APOP.
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Analysis
by VulDB Data Team • 07/26/2018
The vulnerability identified as CVE-2006-2346 affects vpopmail versions 5.4.14 and 5.4.15 when cleartext passwords are enabled in the system configuration. This represents a significant authentication bypass flaw that undermines the security model of email server implementations relying on these versions. The vulnerability specifically targets the authentication mechanisms used in SMTP and APOP protocols, which are fundamental components of email server security infrastructure. The flaw enables remote attackers to gain unauthorized access to user accounts that lack cleartext password configurations by exploiting a simple blank password authentication technique. This issue directly impacts the integrity of email server authentication systems and represents a critical weakness in the security architecture of affected systems.
The technical root cause of this vulnerability lies in the improper handling of authentication requests when cleartext passwords are enabled but no actual password is configured for a user account. The vpopmail implementation fails to properly validate authentication attempts when a blank password is submitted against accounts without cleartext passwords, creating an authentication bypass condition. This flaw operates at the protocol level where SMTP AUTH and APOP mechanisms are processed, allowing attackers to exploit the system's failure to distinguish between legitimate authentication attempts and malicious blank password submissions. The vulnerability is classified as a weakness in authentication mechanisms and falls under the broader category of credential validation failures. According to CWE classification, this represents a weakness in the design or implementation of authentication systems where proper validation of authentication credentials fails to account for edge cases in password configuration states.
The operational impact of CVE-2006-2346 extends beyond simple unauthorized access, potentially enabling attackers to compromise entire email domains and access sensitive user communications. Remote attackers can exploit this vulnerability from any location without requiring local system access or prior credentials, making it particularly dangerous for email server administrators. The vulnerability affects the core email authentication services and can lead to data breaches, unauthorized email forwarding, and potential use as a stepping stone for further attacks within the network infrastructure. Organizations relying on vpopmail versions 5.4.14 and 5.4.15 with cleartext passwords enabled face significant risk of unauthorized access to their email systems, potentially affecting thousands of user accounts simultaneously. This vulnerability directly impacts the confidentiality and integrity of email communications and represents a serious threat to email server security posture.
Mitigation strategies for this vulnerability require immediate action from system administrators to address the authentication bypass condition. The most effective immediate solution involves disabling cleartext password support in vpopmail configurations when it is not strictly required for legacy application compatibility. System administrators should also implement proper account management policies to ensure that user accounts have properly configured passwords rather than relying on blank authentication states. Network-level protections such as firewall rules and access control lists can help limit exposure by restricting access to email authentication ports from trusted networks only. Additionally, implementing monitoring and logging for authentication attempts can help detect exploitation attempts and provide forensic evidence for security incident response. Organizations should also consider upgrading to patched versions of vpopmail or migrating to more modern email server implementations that properly address authentication validation issues. The vulnerability aligns with ATT&CK technique T1110.003 which involves credential stuffing and password guessing, but specifically targets the authentication implementation rather than brute force approaches, making it a more subtle but equally dangerous threat vector.