CVE-2018-0686 in Denbun
Summary
by MITRE
Denbun by NEOJAPAN Inc. (Denbun POP version V3.3P R4.0 and earlier, Denbun IMAP version V3.3I R4.0 and earlier) allows remote authenticated attackers to upload and execute any executable files via unspecified vectors.
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Analysis
by VulDB Data Team • 04/13/2020
The vulnerability identified as CVE-2018-0686 affects Denbun by NEOJAPAN Inc. software including both Denbun POP version V3.3P R4.0 and earlier, and Denbun IMAP version V3.3I R4.0 and earlier. This represents a critical security flaw that enables remote authenticated attackers to execute arbitrary code on affected systems through unspecified upload vectors. The vulnerability exists within the software's file handling mechanisms, specifically allowing authenticated users to upload malicious executable files that can then be executed by the system. This type of vulnerability falls under the category of insecure file upload vulnerabilities, which are commonly classified as CWE-434 within the Common Weakness Enumeration framework. The attack vector requires an authenticated user account, which means that an attacker must first obtain valid credentials before exploiting this vulnerability, though the impact remains severe once achieved.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with the ability to establish persistent access to affected systems. When an authenticated user uploads and executes malicious files, the attacker gains the capability to perform various malicious activities including but not limited to data exfiltration, system reconnaissance, privilege escalation, and deployment of additional malware. The vulnerability's potential for remote code execution creates a significant risk to organizations that rely on these email client applications, particularly in environments where users may have elevated privileges or where the applications are used to process sensitive information. This weakness essentially transforms a legitimate user account into a potential foothold for broader system compromise, making it particularly dangerous in enterprise environments where email systems serve as critical communication infrastructure.
Mitigation strategies for CVE-2018-0686 should focus on both immediate remediation and long-term security improvements. Organizations should immediately update to the latest versions of Denbun POP and Denbun IMAP software where patches are available, as this vulnerability was addressed in subsequent releases. Network segmentation and access controls should be implemented to limit the scope of potential exploitation, particularly restricting upload capabilities to only trusted users or systems. Input validation and file type restrictions should be enforced at multiple layers including application-level checks, web server configurations, and network firewalls. The implementation of principle of least privilege should be enforced, ensuring that users have only the minimum necessary permissions to perform their legitimate tasks. Additionally, security monitoring should be enhanced to detect unusual file upload activities, and regular security assessments should be conducted to identify similar vulnerabilities in other software components. This vulnerability aligns with tactics described in the MITRE ATT&CK framework under the T1059 (Command and Scripting Interpreter) and T1078 (Valid Accounts) techniques, highlighting the importance of comprehensive defensive measures that address both authentication and execution vectors.