CVE-2020-37136: ZOC Terminal 7.25.5 DoS Vulnerability

CVE-2020-37136 Overview

CVE-2020-37136 is a denial of service vulnerability affecting ZOC Terminal version 7.25.5. The vulnerability exists in the private key file input field handling, where attackers can cause the application to crash by supplying a specially crafted oversized input buffer. When an attacker overwrites the private key file input with a 2000-byte buffer, the application becomes unresponsive when attempting to create SSH key files, resulting in a complete denial of service condition.

Critical Impact

Attackers can crash ZOC Terminal through a stack-based buffer overflow in the private key file input field, causing service disruption for users relying on this terminal emulator for SSH connectivity.

Affected Products

• ZOC Terminal 7.25.5

Discovery Timeline

• 2026-02-05 - CVE CVE-2020-37136 published to NVD
• 2026-02-05 - Last updated in NVD database

Technical Details for CVE-2020-37136

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow). The flaw resides in how ZOC Terminal processes input data in the private key file field during SSH key file creation operations. The application fails to properly validate the length of user-supplied input before copying it into a fixed-size stack buffer, allowing an attacker to supply an oversized input that exceeds the allocated buffer space.

The attack requires local access and user interaction, as the malicious input must be entered or loaded through the application's user interface. When triggered, the oversized buffer overwrites adjacent stack memory, corrupting critical program data and causing the application to become unresponsive or crash entirely.

Root Cause

The root cause of this vulnerability is improper input validation in the private key file input handling routine. The application allocates a fixed-size buffer on the stack to store the private key file path but does not enforce adequate bounds checking when accepting user input. This allows an attacker to supply input exceeding the buffer's capacity (approximately 2000 bytes triggers the condition), resulting in a classic stack-based buffer overflow that leads to application instability.

Attack Vector

The attack vector is local, requiring the attacker to have access to the ZOC Terminal application interface. The exploitation scenario involves:

1. The attacker accesses the ZOC Terminal SSH key creation functionality
2. The private key file input field is populated with a 2000-byte (or larger) payload
3. When the application processes this input during key file operations, the oversized data overflows the stack buffer
4. The stack corruption causes the application to crash or hang, denying service to legitimate users

The vulnerability requires user interaction (UI:A) as the malicious input must be entered through the application interface. While this limits automated exploitation, it remains a concern in shared workstation environments or scenarios where attackers can manipulate configuration files loaded by the application.

Detection Methods for CVE-2020-37136

Indicators of Compromise

• Unexpected crashes or hangs of the ZOC.exe process during SSH key operations
• Application error logs indicating access violations or memory corruption
• Presence of unusually long strings in SSH key configuration files
• User reports of ZOC Terminal becoming unresponsive when creating or loading SSH keys

Detection Strategies

• Monitor for repeated crashes of ZOC Terminal processes, particularly during SSH-related operations
• Implement application crash reporting to capture and analyze memory dumps for stack overflow signatures
• Deploy endpoint detection solutions capable of identifying buffer overflow exploitation attempts
• Review application event logs for patterns indicating exploitation attempts

Monitoring Recommendations

• Enable Windows Error Reporting (WER) to capture crash data for ZOC Terminal
• Monitor process stability metrics for terminal emulator applications in enterprise environments
• Implement file integrity monitoring on SSH key configuration directories
• Configure SentinelOne's behavioral AI to alert on anomalous application crashes indicating potential exploitation

How to Mitigate CVE-2020-37136

Immediate Actions Required

• Upgrade ZOC Terminal to a patched version if available from the vendor
• Restrict access to workstations running vulnerable versions of ZOC Terminal
• Implement application whitelisting to control who can execute ZOC Terminal
• Review and limit SSH key creation privileges to authorized personnel only

Patch Information

Users should check with Emtec for security updates addressing this vulnerability. Additional technical details are available through the VulnCheck Advisory and Exploit-DB #48292.

Workarounds

• Limit access to the SSH key creation feature to trusted administrators only
• Consider using alternative terminal emulators until a patch is available
• Implement strict access controls on workstations where ZOC Terminal is deployed
• Monitor ZOC Terminal for unusual behavior and restart the application if it becomes unresponsive