CVE-2001-0714 in Sendmail
Summary
by MITRE
Sendmail before 8.12.1, without the RestrictQueueRun option enabled, allows local users to cause a denial of service (data loss) by (1) setting a high initial message hop count option (-h), which causes Sendmail to drop queue entries, (2) via the -qR option, or (3) via the -qS option.
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Analysis
by VulDB Data Team • 10/04/2025
The vulnerability described in CVE-2001-0714 represents a significant denial of service weakness in Sendmail versions prior to 8.12.1 that stems from improper handling of message queue processing. This flaw specifically affects systems where the RestrictQueueRun option remains disabled, creating an exploitable condition that local attackers can leverage to disrupt mail services. The vulnerability operates through three distinct mechanisms that all ultimately result in queue entries being dropped from the mail processing system, leading to potential data loss and service disruption. The attack vector is particularly concerning because it requires only local system access, making it accessible to users who may not have elevated privileges but still possess the ability to execute commands on the mail server.
The technical implementation of this vulnerability involves manipulating Sendmail's hop count tracking mechanism through specific command-line options that force the system to drop messages from the queue. When attackers use the -h option with a high initial message hop count, they trigger Sendmail's internal logic that determines whether to process or discard queue entries based on hop count thresholds. This mechanism was designed to prevent mail loops and ensure proper delivery, but the implementation flaw allows maliciously crafted hop count values to cause legitimate messages to be prematurely discarded. The additional attack vectors through -qR and -qS options demonstrate the comprehensive nature of this vulnerability, as all three approaches exploit the same underlying queue management weakness.
The operational impact of this vulnerability extends beyond simple service disruption to potentially result in permanent data loss within the mail system. When queue entries are dropped due to manipulated hop count values, messages that were in the process of being delivered or were scheduled for future delivery may be permanently lost from the system. This represents a critical security concern for organizations relying on Sendmail for business communications, as the loss of email messages can have significant operational and legal implications. The vulnerability particularly affects systems where mail queue management is critical for business operations, making it a high-priority issue for system administrators to address immediately.
Mitigation strategies for CVE-2001-0714 should focus on implementing the RestrictQueueRun option as the primary defense mechanism, which prevents the queue processing behavior that makes this vulnerability exploitable. System administrators should also consider implementing proper access controls to limit local user privileges on mail servers and monitor for unusual queue processing patterns that might indicate exploitation attempts. Additionally, organizations should ensure that all Sendmail installations are updated to version 8.12.1 or later, as this vulnerability was specifically addressed in subsequent releases. The fix implemented in version 8.12.1 includes enhanced queue management logic that properly validates hop count values and prevents the premature dropping of queue entries. This vulnerability aligns with CWE-400, which covers unrestricted resource consumption, and can be mapped to ATT&CK technique T1499.004 for denial of service through resource consumption, demonstrating the broader implications of improper queue management in mail systems.