CVE-2013-2111 in Dovecot
Summary
by MITRE
The IMAP functionality in Dovecot before 2.2.2 allows remote attackers to cause a denial of service (infinite loop and CPU consumption) via invalid APPEND parameters.
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Analysis
by VulDB Data Team • 03/22/2022
The vulnerability identified as CVE-2013-2111 represents a critical denial of service weakness within Dovecot's IMAP implementation that existed prior to version 2.2.2. This flaw specifically targets the application's handling of APPEND commands within the IMAP protocol, which is fundamental to email server operations and client-server communication. The vulnerability stems from inadequate input validation and parameter handling within the IMAP subsystem, creating a condition where malformed or invalid APPEND parameters can trigger unexpected behavior in the mail server software.
The technical exploitation of this vulnerability occurs when remote attackers send specially crafted APPEND commands containing invalid parameters to a vulnerable Dovecot server. These malformed parameters cause the IMAP processing logic to enter an infinite loop during the parsing and validation stages, resulting in continuous CPU utilization that can exhaust system resources. The flaw demonstrates characteristics consistent with CWE-835, which describes infinite loops or iterations that can lead to denial of service conditions. The vulnerability is particularly concerning because it requires minimal privileges to exploit, as the attack can be launched from any remote location with network access to the IMAP service.
The operational impact of CVE-2013-2111 extends beyond simple service disruption, as it can effectively render email services unavailable to legitimate users while consuming substantial computational resources. Organizations relying on Dovecot for their email infrastructure face potential downtime and degraded service quality when this vulnerability is exploited, particularly in environments where multiple concurrent connections are handled. The infinite loop condition can persist until the system is manually restarted or the specific connection is terminated, making it a significant concern for email service providers and enterprise environments that depend on continuous email availability.
Mitigation strategies for this vulnerability require immediate patching of Dovecot installations to version 2.2.2 or later, where the improper parameter handling has been corrected through enhanced input validation. System administrators should implement network-level access controls to restrict IMAP service access to trusted networks and monitor for unusual connection patterns that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and organizations should consider implementing intrusion detection systems to identify suspicious APPEND command patterns. Additionally, regular security assessments and vulnerability scanning should be conducted to identify other potential weaknesses in email server configurations, as this vulnerability demonstrates the importance of proper input validation in network services.