CVE-2016-10937 in IMAPFilter
Summary
by MITRE
IMAPFilter through 2.6.12 does not validate the hostname in an SSL certificate.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 12/13/2023
CVE-2016-10937 represents a critical security vulnerability in IMAPFilter versions 2.6.12 and earlier, where the application fails to properly validate SSL certificate hostnames during secure connections. This flaw falls under the weakness category of CWE-295, which specifically addresses improper certificate validation, making it a direct descendant of the well-known SSL/TLS certificate validation issues that have plagued numerous network applications. The vulnerability occurs when IMAPFilter establishes secure connections to mail servers, typically through IMAPS or STARTTLS protocols, where the application should verify that the SSL certificate presented by the server matches the expected hostname to prevent man-in-the-middle attacks.
The technical implementation of this vulnerability stems from IMAPFilter's inadequate handling of certificate verification routines during the SSL handshake process. When connecting to mail servers, the application should perform hostname verification to ensure that the certificate's subject name matches the server's actual hostname. However, the flaw allows attackers to potentially present a valid certificate for a different hostname, which the application accepts without proper validation. This creates a dangerous scenario where an attacker could intercept communications between the email client and legitimate mail servers, potentially capturing sensitive email data, authentication credentials, or other confidential information transmitted through the secure connection.
The operational impact of this vulnerability extends beyond simple data interception, as it fundamentally undermines the trust model that secure email communications rely upon. Attackers could exploit this weakness by setting up malicious mail servers with valid certificates for domains they control, tricking users into connecting to these servers instead of legitimate ones. This would enable the attacker to monitor, modify, or steal email communications, particularly affecting users who rely on IMAPFilter for accessing corporate or personal email accounts. The vulnerability is especially concerning in enterprise environments where email security is paramount, as it could lead to significant data breaches and compromise of sensitive business communications.
Mitigation strategies for CVE-2016-10937 should focus on immediate remediation through software updates to versions 2.6.13 or later, which contain proper hostname validation mechanisms. Organizations should also implement additional network-level security controls such as certificate pinning where possible, and consider deploying network monitoring solutions to detect unusual certificate validation behavior. The vulnerability demonstrates the critical importance of proper SSL/TLS implementation practices, aligning with ATT&CK technique T1566 which covers credential harvesting through social engineering and man-in-the-middle attacks. Security administrators should also conduct thorough vulnerability assessments of their email infrastructure to ensure that all components properly validate SSL certificates, as this flaw could potentially be exploited in conjunction with other attacks targeting email systems.