CVE-2019-11500 in Dovecot
Summary
by MITRE
In Dovecot before 2.2.36.4 and 2.3.x before 2.3.7.2 (and Pigeonhole before 0.5.7.2), protocol processing can fail for quoted strings. This occurs because '\0' characters are mishandled, and can lead to out-of-bounds writes and remote code execution.
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Analysis
by VulDB Data Team • 06/20/2025
The vulnerability identified as CVE-2019-11500 represents a critical security flaw affecting Dovecot email server software and its associated Pigeonhole plugin. This vulnerability stems from improper handling of null characters within quoted string processing during protocol operations, creating a pathway for malicious actors to exploit memory corruption issues. The affected versions include Dovecot 2.2.x prior to 2.2.36.4 and 2.3.x prior to 2.3.7.2, alongside Pigeonhole versions before 0.5.7.2, indicating a widespread impact across multiple software releases.
The technical root cause of this vulnerability lies in the protocol processing logic where null characters are not properly sanitized or handled when processing quoted strings. When Dovecot encounters a quoted string containing null characters, the software fails to properly validate or sanitize these inputs, leading to memory corruption patterns that can result in out-of-bounds writes. This memory corruption behavior creates opportunities for attackers to manipulate the program's execution flow and potentially achieve remote code execution. The vulnerability specifically manifests in how the software processes protocol data streams where quoted strings are parsed, making it particularly dangerous in network-facing email server environments.
The operational impact of CVE-2019-11500 extends beyond simple denial of service scenarios, as the potential for remote code execution poses severe security risks to affected systems. Email servers running vulnerable versions of Dovecot become susceptible to exploitation by attackers who can craft malicious protocol requests containing null characters in quoted strings. This vulnerability can be leveraged to execute arbitrary code on the target system with the privileges of the Dovecot process, potentially leading to complete system compromise. Organizations relying on Dovecot for email services face significant risk, as the vulnerability can be exploited remotely without requiring authentication, making it particularly dangerous in internet-facing environments.
Mitigation strategies for this vulnerability center on immediate software updates to patched versions of Dovecot and Pigeonhole. System administrators should prioritize upgrading to Dovecot 2.2.36.4 or later versions, as well as 2.3.7.2 or later for the 2.3.x series, alongside updating Pigeonhole to version 0.5.7.2 or higher. Additionally, network segmentation and firewall rules should be implemented to restrict access to Dovecot services where possible, while monitoring for suspicious protocol activity. The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and may map to ATT&CK technique T1059 for remote code execution through protocol manipulation. Organizations should also consider implementing intrusion detection systems to monitor for exploitation attempts and maintain comprehensive backup and recovery procedures to address potential compromise scenarios.