CVE-2014-3430 in Dovecot
Summary
by MITRE
Dovecot 1.1 before 2.2.13 and dovecot-ee before 2.1.7.7 and 2.2.x before 2.2.12.12 does not properly close old connections, which allows remote attackers to cause a denial of service (resource consumption) via an incomplete SSL/TLS handshake for an IMAP/POP3 connection.
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Analysis
by VulDB Data Team • 12/17/2024
This vulnerability in Dovecot represents a classic resource exhaustion flaw that has significant implications for email server security and availability. The issue affects multiple versions of the Dovecot IMAP and POP3 server software, specifically targeting the connection handling mechanism during SSL/TLS handshake processes. The vulnerability stems from the software's failure to properly terminate or close old connections that are left in an incomplete state during the SSL/TLS handshake phase, creating a persistent resource leak that can be exploited by remote attackers.
The technical flaw manifests when an attacker establishes an IMAP or POP3 connection to the Dovecot server and initiates an SSL/TLS handshake but deliberately leaves it incomplete or terminates the connection abruptly. The server maintains these incomplete connections in memory without properly cleaning them up, leading to gradual resource consumption over time. This behavior is classified as a resource leak vulnerability and can be categorized under CWE-400, which specifically addresses unspecified resource management issues in software systems. The vulnerability is particularly dangerous because it operates at the protocol level where legitimate connection establishment occurs, making it difficult to distinguish between malicious and legitimate connection attempts.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromise entire email infrastructure availability. As the number of incomplete connections accumulates, the server experiences increasing memory consumption and connection handling overhead, eventually leading to service unavailability for legitimate users. Attackers can leverage this vulnerability by repeatedly initiating incomplete SSL/TLS handshakes, causing the server to consume increasing amounts of system resources until the service becomes unresponsive or crashes entirely. This type of attack aligns with ATT&CK technique T1499.004, which covers network denial of service attacks targeting service availability through resource exhaustion.
Mitigation strategies for this vulnerability require immediate patching of affected Dovecot installations to versions that properly handle connection cleanup during incomplete SSL/TLS handshakes. System administrators should implement connection rate limiting and monitoring to detect unusual connection patterns that may indicate exploitation attempts. Additionally, configuring proper connection timeouts and implementing connection pooling mechanisms can help reduce the window of opportunity for attackers to exploit this vulnerability. The fix implemented in affected versions addresses the core issue by ensuring that incomplete connections are properly closed and cleaned up, preventing the accumulation of stale connection resources that would otherwise lead to the resource exhaustion condition.