CVE-2008-4907 in Dovecot
Summary
by MITRE
The message parsing feature in Dovecot 1.1.4 and 1.1.5, when using the FETCH ENVELOPE command in the IMAP client, allows remote attackers to cause a denial of service (persistent crash) via an email with a malformed From address, which triggers an assertion error, aka "invalid message address parsing bug."
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Analysis
by VulDB Data Team • 12/21/2024
The vulnerability identified as CVE-2008-4907 represents a critical denial of service flaw within Dovecot's IMAP implementation that specifically targets the message parsing functionality. This issue affects Dovecot versions 1.1.4 and 1.1.5, where the FETCH ENVELOPE command processing becomes susceptible to malformed input that can trigger persistent system crashes. The vulnerability stems from inadequate validation of email address formats during message envelope parsing, creating a scenario where remote attackers can exploit this weakness to disrupt service availability. The flaw manifests when an attacker crafts an email message containing a malformed From address that causes the IMAP server to encounter an assertion error during processing, leading to repeated system failures.
The technical mechanism behind this vulnerability involves the improper handling of malformed email addresses within the IMAP FETCH ENVELOPE command execution path. When Dovecot processes an email message with an invalid From address format, the internal message parsing routines fail to properly validate the address structure, resulting in an assertion failure that terminates the process. This assertion error creates a persistent crash condition because the system does not recover gracefully from the malformed input, instead requiring manual intervention to restart the IMAP service. The vulnerability is classified under CWE-129 as an insufficient input validation issue, specifically targeting the parsing of email address formats within a mail server environment.
The operational impact of this vulnerability extends beyond simple service disruption to create significant reliability concerns for email infrastructure. Organizations relying on Dovecot for IMAP services face the risk of persistent system unavailability when attackers exploit this weakness, potentially affecting thousands of users simultaneously. The vulnerability's remote exploitability means that attackers do not require local access or authentication to trigger the denial of service condition, making it particularly dangerous in production environments. The persistent nature of the crashes can overwhelm system monitoring and alerting mechanisms, as the service repeatedly fails and requires manual restart procedures.
Mitigation strategies for CVE-2008-4907 primarily focus on immediate version upgrades to patched Dovecot releases that address the message parsing flaw. System administrators should prioritize updating to Dovecot versions that contain proper input validation for email addresses and enhanced error handling for malformed data. Additional protective measures include implementing network-level filtering to restrict access to IMAP services, deploying intrusion detection systems that can identify malformed email address patterns, and establishing automated monitoring for service availability. The vulnerability demonstrates the importance of robust input validation in mail server implementations and aligns with ATT&CK technique T1499.004 for network denial of service attacks, emphasizing the need for defensive measures against malformed input processing in enterprise email systems.