CVE-2009-3235 in Dovecot
Summary
by MITRE
Multiple stack-based buffer overflows in the Sieve plugin in Dovecot 1.0 before 1.0.4 and 1.1 before 1.1.7, as derived from Cyrus libsieve, allow context-dependent attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted SIEVE script, as demonstrated by forwarding an e-mail message to a large number of recipients, a different vulnerability than CVE-2009-2632.
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Analysis
by VulDB Data Team • 08/22/2021
The vulnerability identified as CVE-2009-3235 represents a critical stack-based buffer overflow flaw within the Sieve plugin of Dovecot email server software. This vulnerability affects versions prior to 1.0.4 and 1.1.7, stemming from the Cyrus libsieve library implementation. The flaw manifests when processing crafted SIEVE scripts, which are used for email filtering and automation within the Dovecot environment. The vulnerability is particularly concerning because it operates in a context-dependent manner, meaning that successful exploitation requires specific conditions to be met by the attacker.
The technical implementation of this vulnerability involves improper bounds checking within the Sieve plugin's handling of email forwarding operations. When a SIEVE script containing maliciously crafted elements is processed, particularly during the forwarding of email messages to multiple recipients, the application fails to validate the size of input data against allocated stack buffer space. This allows an attacker to overflow the stack buffer and potentially overwrite adjacent memory locations, leading to unpredictable behavior including application crashes or more severe exploitation opportunities. The vulnerability specifically leverages the email forwarding functionality, making it particularly dangerous in environments where automated email processing is common.
The operational impact of CVE-2009-3235 extends beyond simple denial of service scenarios, as the vulnerability may enable remote code execution under certain conditions. The context-dependent nature of the flaw means that attackers must carefully craft SIEVE scripts to exploit the vulnerability effectively, typically involving complex forwarding operations with large recipient lists. This creates a scenario where legitimate email processing operations can be weaponized, making detection and prevention challenging for system administrators. The vulnerability affects the core email filtering functionality of Dovecot, potentially compromising the integrity and availability of email services across affected systems.
Mitigation strategies for this vulnerability require immediate patching of Dovecot installations to versions 1.0.4 or 1.1.7 and later, which contain the necessary fixes for the buffer overflow conditions. Organizations should also implement strict SIEVE script validation and sanitization procedures, particularly for scripts that handle large recipient lists or complex forwarding operations. Network monitoring should be enhanced to detect unusual email forwarding patterns that might indicate exploitation attempts. From a cybersecurity perspective, this vulnerability aligns with CWE-121 stack-based buffer overflow classification and represents a potential attack vector within the ATT&CK framework's execution and privilege escalation domains. System administrators should also consider implementing additional security controls such as email content filtering and rate limiting to reduce the attack surface and prevent exploitation of similar vulnerabilities in the future.