CVE-2018-16745 in Mgetty
Summary
by MITRE
An issue was discovered in mgetty before 1.2.1. In fax_notify_mail() in faxrec.c, the mail_to parameter is not sanitized. It could allow a buffer overflow if long untrusted input can reach it.
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Analysis
by VulDB Data Team • 03/23/2020
The vulnerability identified as CVE-2018-16745 represents a critical buffer overflow flaw within the mgetty package version 1.2.0 and earlier. This issue resides in the fax_notify_mail() function located in the faxrec.c source file, where the mail_to parameter undergoes insufficient input validation and sanitization. The mgetty utility serves as aGetty implementation specifically designed for handling modem connections and fax communications, making it a crucial component in systems that manage telephony services and fax processing. When untrusted input reaches the mail_to parameter without proper sanitization, the application becomes susceptible to memory corruption that can potentially lead to arbitrary code execution or system compromise.
This vulnerability falls under the CWE-121 category of Stack-based Buffer Overflow, which occurs when a program writes more data to a fixed-length buffer than it can hold, causing adjacent memory locations to be overwritten. The flaw specifically manifests in the faxrec.c file where the fax_notify_mail() function processes email addresses for fax notification purposes. The lack of proper input validation means that attackers can craft maliciously long input strings that exceed the allocated buffer space, triggering the buffer overflow condition. This type of vulnerability is particularly dangerous in telephony and fax systems because these applications often run with elevated privileges and may be accessible through network interfaces or modem connections.
The operational impact of this vulnerability extends beyond simple denial of service scenarios. An attacker who successfully exploits this buffer overflow could potentially execute arbitrary code on the target system with the privileges of the mgetty process. This could lead to complete system compromise, especially if the fax processing service is running with root privileges or has access to sensitive system resources. The vulnerability is particularly concerning in environments where fax services are exposed to untrusted networks or where users can submit fax jobs through web interfaces or other external means. The buffer overflow could also be leveraged to cause application crashes, leading to denial of service conditions that disrupt legitimate fax communications and telephony services.
Mitigation strategies for CVE-2018-16745 primarily focus on immediate patching of the mgetty package to version 1.2.1 or later, which contains the necessary input sanitization fixes. System administrators should also implement additional protective measures such as restricting network access to fax services, implementing proper input validation at multiple layers, and monitoring for unusual fax processing activities. The vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: PowerShell, though the specific exploitation would likely occur through buffer overflow techniques rather than PowerShell specifically. Network segmentation and access controls should be implemented to limit exposure of fax services to untrusted networks, while regular security audits should verify that all telephony and fax processing components have been updated to their latest secure versions. The fix implemented in mgetty 1.2.1 ensures proper bounds checking and input sanitization for the mail_to parameter, preventing the buffer overflow condition from occurring.