CVE-2002-2253 in Sieve
Summary
by MITRE
Multiple buffer overflows in Cyrus Sieve / libSieve 2.1.2 and earlier allow remote attackers to execute arbitrary code via (1) a long header name, (2) a long IMAP flag, or (3) a script that generates a large number of errors that overflow the resulting error string.
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Analysis
by VulDB Data Team • 04/20/2019
The vulnerability identified as CVE-2002-2253 represents a critical security flaw in Cyrus Sieve and libSieve versions 2.1.2 and earlier, which are components of the Cyrus IMAP server suite widely used for email management and automation. This vulnerability falls under the category of buffer overflow conditions that can be exploited remotely to execute arbitrary code on affected systems. The flaw specifically affects the processing of email headers, IMAP flags, and error string generation within the Sieve script execution environment, making it particularly dangerous for email servers that process untrusted input from external sources.
The technical implementation of this vulnerability stems from inadequate input validation and bounds checking within the Sieve script interpreter. When processing email headers, the system fails to properly validate the length of header names, allowing attackers to craft malicious messages with excessively long header fields that exceed the allocated buffer space. Similarly, the IMAP flag processing mechanism does not enforce length limitations on flag values, creating another vector for buffer overflow exploitation. The third vulnerability occurs during error string generation where scripts that produce numerous errors can cause the error handling mechanism to overflow its allocated memory space. These buffer overflows occur because the software does not implement proper bounds checking before copying data into fixed-length buffers, directly violating secure coding practices outlined in the CWE-121 category for stack-based buffer overflow conditions.
The operational impact of this vulnerability extends far beyond simple denial of service scenarios, as it provides remote attackers with the capability to execute arbitrary code with the privileges of the affected service. This could result in complete system compromise, data theft, or unauthorized access to email communications. Email servers running vulnerable versions of Cyrus Sieve are particularly at risk since they routinely process messages from untrusted sources, making them attractive targets for exploitation. The vulnerability affects systems where Sieve scripts are enabled for email filtering and automation, which are common in enterprise email environments and mail hosting services. Attackers could leverage this vulnerability to gain persistent access to email infrastructure, potentially leading to widespread data breaches or disruption of email services across organizations.
Mitigation strategies for CVE-2002-2253 should prioritize immediate patching of affected systems with updated versions of Cyrus Sieve and libSieve that include proper input validation and buffer size enforcement. Organizations should also implement network segmentation and access controls to limit exposure of vulnerable services to untrusted networks. The implementation of input validation mechanisms, including length restrictions on email headers and IMAP flags, along with proper error handling that prevents overflow conditions, forms the foundation of defensive measures. Security monitoring should include detection of unusual error message patterns and header lengths that might indicate exploitation attempts. Additionally, organizations should consider implementing intrusion detection systems that can identify suspicious patterns in email processing activities and maintain regular vulnerability assessments to identify other potential buffer overflow conditions within their email infrastructure. The vulnerability aligns with ATT&CK techniques related to remote code execution and privilege escalation, making it a high-priority target for security hardening efforts.