Executive Summary

CVE-2018-25251 is a buffer overflow vulnerability in Snes9K version 0.0.9z, specifically in the Netplay Socket Port Number field. Local attackers can exploit this by inputting a specially crafted payload into this field via the Netplay Options menu.

The vulnerability allows attackers to overwrite the Structured Exception Handler (SEH) chain, which can be manipulated to execute arbitrary code on the affected system.

This exploit involves crafting a buffer that includes NOPs, a short jump instruction, an SEH overwrite pointing to a POP-POP-RET sequence, and shellcode that can spawn a shell bound to a TCP port, enabling code execution locally.

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Impact Analysis

This vulnerability can lead to local arbitrary code execution on the affected system without requiring privileges or user interaction.

An attacker exploiting this flaw can execute malicious code, potentially leading to full system compromise, including confidentiality, integrity, and availability impacts.

• Local privilege escalation or arbitrary code execution.
• Potential unauthorized access to sensitive data.
• Disruption or denial of service due to system instability.

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Detection Guidance

This vulnerability can be detected by checking if the Snes9K version 0.0.9z or earlier is installed and by monitoring for attempts to input unusual or crafted payloads into the Netplay Socket Port Number field via the Netplay Options menu.

Since the exploit involves local input of a malicious payload into the Socket Port Number field and subsequent connection on TCP port 4444, you can monitor local system activity for suspicious usage of the Snes9K application and network connections on port 4444.

• Check the installed version of Snes9K to confirm if it is 0.0.9z or earlier.
• Monitor local processes for execution of Snes9K and unusual input activity in the Netplay Options menu.
• Use network monitoring tools to detect inbound or outbound connections on TCP port 4444, which is used by the exploit shellcode.
• Example command to check for listening connections on port 4444 (on Windows): netstat -ano | findstr :4444
• Example command to check running processes for Snes9K (on Windows): tasklist | findstr snes9k

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Mitigation Strategies

To mitigate this vulnerability immediately, you should avoid running Snes9K version 0.0.9z or earlier, especially on systems where local users can access the Netplay Options menu.

Restrict local access to the vulnerable application to trusted users only, and monitor or block network connections on TCP port 4444 to prevent exploitation.

If possible, update to a fixed or newer version of Snes9K that addresses this buffer overflow vulnerability.

As a temporary workaround, avoid using the Netplay Socket Port Number field or validate and sanitize inputs to this field to prevent malicious payloads.

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Compliance Impact

The vulnerability allows local attackers to achieve code execution with high impact on confidentiality, integrity, and availability of the affected system.

Such a compromise could lead to unauthorized access or manipulation of sensitive data, which may result in non-compliance with data protection regulations like GDPR or HIPAA that require safeguarding confidentiality and integrity of personal or health information.

However, there is no explicit information provided about direct compliance impact or mitigation measures related to these standards.

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