CVE-2016-7115 in MAC-Telnet
Summary
by MITRE
Buffer overflow in the handle_packet function in mactelnet.c in the client in MAC-Telnet 0.4.3 and earlier allows remote TELNET servers to execute arbitrary code via a long string in an MT_CPTYPE_PASSSALT control packet.
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Analysis
by VulDB Data Team • 09/14/2022
The vulnerability identified as CVE-2016-7115 represents a critical buffer overflow flaw within the MAC-Telnet client software version 0.4.3 and earlier. This issue resides in the handle_packet function located within the mactelnet.c source file, creating a significant security risk that can be exploited by remote attackers. The vulnerability specifically targets the client-side implementation of the MAC-Telnet protocol, which is designed to provide network access control through MAC address authentication rather than traditional username/password authentication methods.
The technical flaw manifests when the client processes MT_CPTYPE_PASSSALT control packets from remote TELNET servers. This control packet type is intended to carry password salt information for authentication purposes, but the implementation fails to properly validate the length of incoming data. When a malicious server sends a control packet containing an excessively long string, the buffer allocated to store this data becomes overflowed, allowing arbitrary code execution on the vulnerable client system. This represents a classic buffer overflow vulnerability that falls under the CWE-121 category of stack-based buffer overflow, where insufficient bounds checking permits data to overwrite adjacent memory locations.
The operational impact of this vulnerability extends beyond simple remote code execution, as it can be leveraged to completely compromise the client system. An attacker positioned to intercept or manipulate network traffic between a client and server can exploit this flaw to gain unauthorized access to the client machine, potentially escalating privileges or establishing persistent backdoors. The vulnerability affects any system running MAC-Telnet client software version 0.4.3 or earlier, making it particularly concerning for enterprise environments where such authentication systems might be deployed. This issue aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation would enable attackers to execute arbitrary commands on the compromised system.
Mitigation strategies for this vulnerability require immediate software updates to MAC-Telnet versions that address the buffer overflow issue through proper input validation and bounds checking. Organizations should implement network segmentation and monitoring to detect unusual control packet traffic patterns that might indicate exploitation attempts. Additionally, the use of alternative authentication methods or network access control systems should be considered as temporary measures while implementing proper patches. Security teams should also conduct vulnerability assessments to identify all systems running affected MAC-Telnet client versions and establish monitoring procedures to detect potential exploitation attempts. The vulnerability demonstrates the importance of proper input validation in network protocol implementations and highlights the risks associated with legacy authentication systems that may not receive regular security updates.