CVE-2019-25589: ZOC Terminal Buffer Overflow Vulnerability

CVE-2019-25589 Overview

CVE-2019-25589 is a buffer overflow vulnerability affecting ZOC Terminal version 7.23.4. The flaw exists in the Shell field within the Program Settings functionality, allowing local attackers to crash the application by supplying an excessively long string. An attacker can paste a crafted payload into the Shell configuration field and trigger a denial of service condition when accessing the Command Shell feature.

Critical Impact

Local attackers can cause application crashes and denial of service by exploiting improper buffer handling in the ZOC Terminal Shell configuration field.

Affected Products

• ZOC Terminal version 7.23.4

Discovery Timeline

• 2026-03-22 - CVE CVE-2019-25589 published to NVD
• 2026-03-23 - Last updated in NVD database

Technical Details for CVE-2019-25589

Vulnerability Analysis

This vulnerability is classified under CWE-787 (Out-of-bounds Write), which occurs when the software writes data past the end, or before the beginning, of the intended buffer. In the context of ZOC Terminal, the application fails to properly validate the length of user-supplied input in the Shell configuration field before copying it to a fixed-size buffer.

When a user pastes an excessively long string into the Shell field within Program Settings, the application attempts to process this input without adequate bounds checking. This results in memory corruption that leads to an application crash. While the current classification indicates a denial of service condition with high availability impact, buffer overflow vulnerabilities can potentially be leveraged for more severe exploits depending on the memory layout and protection mechanisms in place.

The vulnerability requires local access to exploit, as an attacker must be able to interact with the ZOC Terminal application's configuration interface directly.

Root Cause

The root cause of CVE-2019-25589 is insufficient input validation in the Shell field handler within ZOC Terminal's Program Settings module. The application allocates a fixed-size buffer for storing the Shell path but does not enforce appropriate length restrictions on user input before copying the data. This allows attackers to provide input that exceeds the buffer's capacity, resulting in an out-of-bounds write condition that corrupts adjacent memory and crashes the application.

Attack Vector

The attack vector for this vulnerability is local, requiring an attacker to have direct access to the ZOC Terminal application. The exploitation process involves:

1. Opening ZOC Terminal and navigating to Program Settings
2. Locating the Shell configuration field
3. Pasting an excessively long crafted string into the Shell field
4. Triggering the Command Shell feature, which causes the buffer overflow and subsequent application crash

The vulnerability can be exploited by any local user with access to the application's settings interface. No authentication bypass or privilege escalation is required to trigger the condition, though the impact is limited to denial of service affecting application availability.

Technical details and proof-of-concept information can be found in the Exploit-DB #46857 and the VulnCheck ZOC Advisory.

Detection Methods for CVE-2019-25589

Indicators of Compromise

• Unexpected ZOC Terminal application crashes, particularly when accessing Command Shell functionality
• Abnormally long strings present in ZOC Terminal configuration files or registry entries
• Application crash logs indicating memory access violations in ZOC Terminal processes
• Evidence of configuration tampering in ZOC Terminal Program Settings

Detection Strategies

• Monitor for ZOC Terminal process crashes and analyze associated crash dumps for buffer overflow indicators
• Implement application whitelisting and configuration monitoring to detect unauthorized changes to Shell settings
• Deploy endpoint detection solutions that can identify memory corruption attempts in desktop applications
• Enable Windows Error Reporting to capture detailed crash information for forensic analysis

Monitoring Recommendations

• Configure endpoint monitoring to alert on repeated ZOC Terminal crashes or restarts
• Monitor system event logs for application fault events related to ZOC Terminal (zoc.exe)
• Implement file integrity monitoring on ZOC Terminal configuration files
• Use SentinelOne's behavioral AI to detect anomalous process behavior patterns associated with buffer overflow exploitation

How to Mitigate CVE-2019-25589

Immediate Actions Required

• Upgrade ZOC Terminal to the latest available version from Emtec's official website
• Restrict local access to systems running vulnerable versions of ZOC Terminal
• Implement application control policies to prevent unauthorized modification of ZOC Terminal settings
• Consider temporarily disabling or restricting access to the Command Shell feature if not required

Patch Information

Users should download the latest version of ZOC Terminal from the Emtec official download page or visit the Emtec homepage to check for security updates addressing this vulnerability. Organizations should verify they are running a patched version that includes proper input validation for the Shell configuration field.

Workarounds

• Limit physical and remote access to workstations running ZOC Terminal to trusted users only
• Use application sandboxing or containerization to isolate ZOC Terminal from critical system resources
• Implement endpoint protection solutions with memory exploit prevention capabilities
• Monitor and restrict clipboard operations that could be used to paste malicious payloads into application fields

# Verify ZOC Terminal version and check for updates
# Windows PowerShell command to check installed version
Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*" | 
  Where-Object { $_.DisplayName -like "*ZOC*" } | 
  Select-Object DisplayName, DisplayVersion