Stack Buffer Underwrite in Ettercap Telnet Dissector

Executive Summary

Ettercap through 0.8.4.1 has a stack buffer underwrite flaw in its telnet dissector. The vulnerability occurs when the output pointer is decremented on backspace without checking if it goes below the buffer's lower bound. Attackers exploit this by sending a telnet stream with more backspaces than preceding characters, causing the Ettercap process to write below the stack buffer and corrupt its stack.

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Detection Guidance

Detect Ettercap instances running on your network by checking for processes named 'ettercap' using commands like 'ps aux | grep ettercap' or 'pgrep ettercap'. Monitor network traffic for unusual telnet protocol activity, especially streams with excessive backspace characters, using tools like Wireshark with filters such as 'tcp.port==23'.

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Impact Analysis

This vulnerability allows attackers to corrupt the stack of the Ettercap process, which typically runs with root privileges. Successful exploitation could lead to arbitrary code execution, denial of service, or privilege escalation on the affected system.

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Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data transmitted over telnet sessions, such as credentials or personal information. For GDPR, this may result in breaches of personal data requiring notification under Articles 33-34. For HIPAA, it could expose protected health information, violating the Security Rule's integrity and confidentiality requirements.

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Mitigation Strategies

Immediately update Ettercap to the latest version beyond 0.8.4.1. Disable or restrict telnet protocol usage on your network. Implement network segmentation to isolate Ettercap traffic. Monitor system logs for signs of exploitation and consider disabling Ettercap services if not essential.

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