CVE-2019-7524 in Dovecot
Summary
by MITRE
In Dovecot before 2.2.36.3 and 2.3.x before 2.3.5.1, a local attacker can cause a buffer overflow in the indexer-worker process, which can be used to elevate to root. This occurs because of missing checks in the fts and pop3-uidl components.
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Analysis
by VulDB Data Team • 08/17/2023
The vulnerability identified as CVE-2019-7524 represents a critical buffer overflow flaw in Dovecot email server software that affects versions prior to 2.2.36.3 and 2.3.5.1. This vulnerability exists within the indexer-worker process which is responsible for handling full-text search indexing operations and pop3 uidl functionality. The flaw stems from insufficient input validation and boundary checking mechanisms in the fts (full text search) and pop3-uidl components, creating a pathway for malicious exploitation that could lead to privilege escalation.
The technical implementation of this vulnerability occurs when the indexer-worker process handles malformed input data through the fts and pop3-uidl modules. When these components process untrusted data without proper bounds checking, they fail to validate the size or format of incoming buffers, allowing an attacker to overflow allocated memory spaces. This buffer overflow condition specifically targets memory regions controlled by the indexer-worker process which runs with elevated privileges, particularly when the process is executed with root permissions. The missing validation checks create a scenario where attacker-controlled input can overwrite adjacent memory locations, potentially corrupting program execution flow or allowing arbitrary code execution.
From an operational perspective, this vulnerability presents a severe risk to email server security infrastructure as it allows local attackers to escalate privileges from regular user accounts to root access. The exploitation requires local system access but provides a significant attack vector for malicious actors who have already gained initial access to the system. The impact extends beyond simple privilege escalation since Dovecot typically handles sensitive email data, making the potential compromise of the entire email infrastructure a serious concern. Organizations running affected Dovecot versions face the risk of complete system compromise where attackers can access all email accounts, modify email content, or establish persistent backdoors.
The vulnerability aligns with CWE-121 Stack-based Buffer Overflow and CWE-122 Heap-based Buffer Overflow classifications, representing a classic memory corruption issue that enables privilege escalation. From the ATT&CK framework perspective, this vulnerability maps to T1068 Privilege Escalation and T1059 Command and Scripting Interpreter techniques, as attackers would leverage the buffer overflow to execute arbitrary commands with elevated privileges. The attack chain typically begins with local access, followed by exploitation of the buffer overflow to gain root privileges, and concludes with full system compromise. Organizations should prioritize immediate patching of affected Dovecot installations and implement monitoring for suspicious indexer-worker process behavior. Additional mitigations include running Dovecot processes with reduced privileges where possible, implementing proper input validation, and conducting regular security assessments to identify similar memory corruption vulnerabilities in other email server components.