CVE-2020-10957 in Dovecot
Summary
by MITRE
In Dovecot before 2.3.10.1, unauthenticated sending of malformed parameters to a NOOP command causes a NULL Pointer Dereference and crash in submission-login, submission, or lmtp.
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Analysis
by VulDB Data Team • 10/18/2020
The vulnerability identified as CVE-2020-10957 represents a critical NULL pointer dereference issue affecting Dovecot email servers prior to version 2.3.10.1. This flaw resides in the handling of malformed parameters within the NOOP command, which is a standard command used in email protocols to maintain connection state. The vulnerability specifically impacts the submission-login, submission, and lmtp services, which are essential components for email submission and delivery within mail server infrastructure. The issue stems from insufficient input validation and parameter handling within Dovecot's protocol parsing mechanisms, creating a scenario where unauthenticated attackers can trigger a crash condition through carefully crafted malformed parameters.
The technical execution of this vulnerability involves sending specially crafted NOOP commands with malformed parameters to Dovecot services. When these commands are processed, the server attempts to dereference a NULL pointer during parameter parsing, leading to an immediate crash of the affected service process. This type of vulnerability falls under CWE-476, which specifically addresses NULL Pointer Dereference conditions in software implementations. The crash occurs in the context of email submission services, meaning that attackers can potentially disrupt email delivery and submission capabilities without requiring authentication credentials. The affected services include submission-login which handles user authentication for email submission, submission which manages the actual email submission process, and lmtp which handles local mail transfer protocol operations. The operational impact is significant as these services form the backbone of email delivery infrastructure in many organizations.
From an operational perspective, this vulnerability presents a severe risk to email server availability and reliability. The crash condition affects multiple core email services, potentially causing widespread disruption to email communication within affected organizations. The unauthenticated nature of the attack means that any external party can exploit this vulnerability without requiring valid credentials, making it particularly dangerous in environments where email servers are exposed to public networks. The vulnerability aligns with ATT&CK technique T1499.004 which covers network disruption attacks, specifically targeting email services and their availability. Organizations running vulnerable versions of Dovecot face the risk of service degradation or complete outages, which can severely impact business operations and communication workflows. The crash condition typically results in process termination and requires manual intervention to restore service availability, creating additional operational overhead.
Mitigation strategies for CVE-2020-10957 primarily focus on upgrading to Dovecot version 2.3.10.1 or later, which contains the necessary patches to address the NULL pointer dereference issue. Organizations should implement immediate patch management procedures to update all affected Dovecot installations across their infrastructure. Network-level protections can include implementing firewall rules to restrict access to email submission ports, though this approach is less effective given the vulnerability's unauthenticated nature. Additional protective measures involve monitoring for suspicious NOOP command patterns and implementing intrusion detection systems that can identify malformed parameter sequences targeting this specific vulnerability. Security teams should also consider implementing service redundancy and failover mechanisms to minimize the impact of potential crashes. The vulnerability highlights the importance of thorough input validation and proper error handling in network service implementations, particularly for protocols that handle user-provided data. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other email server components and related software systems.