CVE-1999-0194 in Host
Summary
by MITRE
Denial of service in in.comsat allows attackers to generate messages.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability identified as CVE-1999-0194 represents a denial of service condition within the in.comsat service, which is part of the Sendmail suite of email services. This flaw specifically affects the comsat daemon that handles incoming mail notifications and message processing. The vulnerability stems from inadequate input validation and message handling mechanisms within the service, allowing malicious actors to craft specially formatted messages that trigger abnormal service behavior. The affected in.comsat service operates as a mail notification daemon that monitors mail queues and forwards notifications to users, making it a critical component in email infrastructure management.
The technical flaw manifests when the in.comsat daemon processes malformed or specially crafted messages that exceed expected parameter limits or contain unexpected data structures. This processing error causes the service to enter an unstable state where it either crashes completely or becomes unresponsive to legitimate mail processing tasks. The vulnerability exploits a weakness in the service's message parsing logic, where insufficient bounds checking and validation allows attacker-controlled data to disrupt normal service operations. This type of flaw falls under CWE-129 Input Validation and CWE-20 General Input Validation, representing a classic example of improper input sanitization that leads to service disruption.
The operational impact of this vulnerability extends beyond simple service interruption, as it can affect the entire email delivery infrastructure that relies on the comsat daemon for proper notification handling. When the in.comsat service becomes unavailable or unstable, users may experience delays in receiving mail notifications, and system administrators might face difficulties in monitoring mail queue status. The vulnerability is particularly concerning because it allows remote attackers to trigger service degradation without requiring authentication or elevated privileges, making it a significant threat to email system reliability. This aligns with ATT&CK technique T1499.004 for Network Denial of Service, where attackers exploit service vulnerabilities to disrupt system availability.
Mitigation strategies for this vulnerability involve implementing proper input validation mechanisms within the in.comsat service, including bounds checking for message parameters and implementing robust error handling procedures. System administrators should ensure that all email services are properly patched and updated to address known vulnerabilities in the Sendmail suite. The recommended approach includes configuring the service to reject malformed messages at the network level and implementing monitoring systems to detect unusual service behavior patterns. Additionally, organizations should consider implementing network segmentation to limit the potential impact of such vulnerabilities and establish redundant notification systems to maintain service availability even when individual components fail. The vulnerability demonstrates the critical importance of input validation in network services and highlights the need for comprehensive security testing of system components that handle external data inputs.