CVE-2009-2632 in Cyrus IMAP Server
Summary
by MITRE
Buffer overflow in the SIEVE script component (sieve/script.c), as used in cyrus-imapd in Cyrus IMAP Server 2.2.13 and 2.3.14, and Dovecot 1.0 before 1.0.4 and 1.1 before 1.1.7, allows local users to execute arbitrary code and read or modify arbitrary messages via a crafted SIEVE script, related to the incorrect use of the sizeof operator for determining buffer length, combined with an integer signedness error.
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Analysis
by VulDB Data Team • 03/30/2025
The vulnerability described in CVE-2009-2632 represents a critical buffer overflow condition affecting email server implementations that utilize SIEVE script processing capabilities. This flaw manifests within the sieve/script.c component of messaging servers, specifically impacting Cyrus IMAP Server versions 2.2.13 and 2.3.14, as well as Dovecot versions prior to 1.0.4 and 1.1.7. The vulnerability stems from improper memory management practices where the sizeof operator is incorrectly applied to determine buffer dimensions, creating an environment where attacker-controlled input can exceed allocated memory boundaries and potentially execute arbitrary code with elevated privileges.
The technical root cause of this vulnerability involves a combination of two distinct programming errors that compound to create a dangerous condition. First, developers incorrectly used the sizeof operator to calculate buffer sizes, which typically returns the size of a data type rather than the actual length of dynamic content. Second, the implementation contains an integer signedness error that allows negative values to be interpreted as positive buffer sizes, effectively bypassing size validation checks. This dual flaw creates a scenario where a maliciously crafted SIEVE script can manipulate memory layout and overwrite adjacent data structures, potentially leading to code execution or data corruption. According to CWE-121, this vulnerability maps directly to stack-based buffer overflow conditions where insufficient bounds checking allows attackers to write beyond allocated memory regions.
The operational impact of CVE-2009-2632 extends beyond simple privilege escalation to encompass complete system compromise and data integrity violations. Local users with access to SIEVE script execution capabilities can leverage this vulnerability to execute arbitrary code at the privilege level of the affected service, potentially enabling full system control. The ability to read or modify arbitrary messages represents a severe confidentiality and integrity threat, as attackers can access sensitive email communications, modify message content, or delete critical data. This vulnerability particularly affects email infrastructure where SIEVE scripts are used for automated message filtering, forwarding, or processing, making it a significant concern for organizations relying on these server implementations for business communications.
Mitigation strategies for CVE-2009-2632 require immediate patch deployment and comprehensive system hardening measures. Organizations should prioritize upgrading to patched versions of Cyrus IMAP Server and Dovecot, specifically versions 2.3.15, 1.0.4, and 1.1.7 respectively, which contain the necessary fixes for the buffer overflow conditions. Additionally, implementing strict input validation for SIEVE scripts and limiting script execution privileges can reduce the attack surface. System administrators should also consider deploying intrusion detection systems that monitor for suspicious SIEVE script execution patterns and implement network segmentation to limit local user access to email server components. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the T1068 privilege escalation sub-technique, where local users exploit software vulnerabilities to gain elevated system access. Organizations should also establish robust patch management processes to prevent similar vulnerabilities from being exploited in other components of their email infrastructure and consider implementing application whitelisting to restrict execution of unauthorized SIEVE scripts.