CVE-2002-1391 in mgetty
Summary
by MITRE
Buffer overflow in cnd-program for mgetty before 1.1.29 allows remote attackers to cause a denial of service and possibly execute arbitrary code via a Caller ID string with a long CallerName argument.
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Analysis
by VulDB Data Team • 07/19/2019
The vulnerability identified as CVE-2002-1391 represents a critical buffer overflow flaw within the cnd-program component of mgetty software versions prior to 1.1.29. This issue manifests specifically when processing Caller ID strings, particularly those containing excessively long CallerName arguments. The mgetty package serves as a crucial component in Unix-based systems for handling modem connections and fax communications, making this vulnerability particularly concerning for network security infrastructure. The buffer overflow vulnerability occurs in the handling of incoming Caller ID data, which is typically transmitted over telephone lines during modem connections and is used by systems to identify calling parties.
The technical implementation of this vulnerability stems from inadequate input validation within the cnd-program module, which processes Caller ID information received from modems. When a malformed Caller ID string containing an overly long CallerName argument is processed, the program fails to properly bounds-check the input data before copying it into fixed-size buffers. This lack of proper boundary checking creates an exploitable condition where attacker-controlled data can overwrite adjacent memory locations in the program's stack. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which can potentially lead to arbitrary code execution when carefully crafted input causes the overflow to overwrite return addresses or other critical program control structures. The flaw exists in the communication handling logic that processes modem data streams, specifically during the parsing of Caller ID protocol messages.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enabling remote code execution, making it a significant threat to system integrity. An attacker capable of sending a specially crafted Caller ID string to a vulnerable mgetty system could cause the cnd-program to crash, resulting in a denial of service that disrupts modem communication services. However, the more severe implications arise from the potential for code execution, where carefully constructed buffer overflow payloads could allow remote attackers to execute arbitrary commands with the privileges of the running process. This vulnerability affects systems that rely on mgetty for modem access and fax services, particularly those connected to public switched telephone networks where Caller ID information is routinely transmitted. The attack vector requires only the ability to send data to a vulnerable system through a modem connection, making it particularly dangerous in environments where modems are exposed to untrusted networks or where Caller ID data is processed without proper sanitization.
Mitigation strategies for CVE-2002-1391 primarily focus on upgrading to mgetty version 1.1.29 or later, which includes proper input validation and bounds-checking mechanisms to prevent the buffer overflow condition. System administrators should also implement network segmentation and access controls to limit exposure of vulnerable systems to untrusted Caller ID data sources. Additional defensive measures include configuring modems to filter or sanitize incoming Caller ID information before it reaches the mgetty processing components, and implementing monitoring solutions to detect anomalous Caller ID data patterns that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1203 (Exploitation for Client Execution) and T1068 (Exploitation for Privilege Escalation), demonstrating how buffer overflow conditions can be leveraged for both service disruption and privilege escalation within affected systems. Organizations should also consider implementing intrusion detection systems that can identify suspicious Caller ID data patterns and ensure that all modem-related services are regularly updated and patched according to security best practices.