CVE-2016-20050: NetSchedScan Buffer Overflow DoS Flaw

CVE-2016-20050 Overview

CVE-2016-20050 is a buffer overflow vulnerability affecting NetSchedScan 1.0 in the scan Hostname/IP input field. The vulnerability allows local attackers to crash the application by supplying an oversized input string. Specifically, attackers can paste a crafted payload containing 388 bytes of data followed by 4 bytes of EIP overwrite into the Hostname/IP field to trigger a denial of service condition.

Critical Impact

Local attackers can exploit this buffer overflow to crash NetSchedScan 1.0, causing a denial of service condition through EIP register overwrite.

Affected Products

• NetSchedScan 1.0

Discovery Timeline

• 2026-04-04 - CVE CVE-2016-20050 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2016-20050

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write), a memory corruption issue that occurs when the application writes data past the end of an allocated buffer. In the context of NetSchedScan 1.0, the scan Hostname/IP input field fails to properly validate the length of user-supplied input before copying it into a fixed-size buffer.

The local attack vector means an attacker requires direct access to the system where NetSchedScan is installed. When an oversized string is provided, the application's stack is corrupted, leading to potential control flow hijacking. The specific payload structure (388 bytes plus 4 bytes for EIP) indicates a classic stack-based buffer overflow where the return address can be overwritten.

While the current exploitation demonstrates denial of service through application crash, the ability to overwrite the EIP (Extended Instruction Pointer) register suggests that with additional exploitation development, arbitrary code execution might be achievable.

Root Cause

The root cause of this vulnerability is improper input validation in the Hostname/IP field processing routine. The application allocates a fixed-size buffer for hostname input but does not enforce boundary checks when copying user-supplied data. This allows attackers to write beyond the allocated buffer space, corrupting adjacent memory including the saved return address on the stack.

Attack Vector

This is a local attack vector vulnerability requiring the attacker to have access to the NetSchedScan application interface. The attack is executed by pasting a specially crafted payload into the Hostname/IP input field. The payload structure consists of 388 bytes of padding data followed by 4 bytes that overwrite the EIP register. When the vulnerable function returns, execution flow is disrupted, causing the application to crash.

The exploitation process involves:

1. Opening the NetSchedScan 1.0 application
2. Navigating to the scan functionality
3. Pasting a crafted 392-byte payload into the Hostname/IP field
4. Triggering the scan operation to execute the vulnerable code path

Technical details and proof-of-concept information are available in the Exploit-DB #39242 advisory.

Detection Methods for CVE-2016-20050

Indicators of Compromise

• Unexpected crashes of the NetSchedScan application with access violation errors
• Application event logs showing memory access violations or stack corruption
• Evidence of unusually long strings in hostname/IP input fields in memory dumps

Detection Strategies

• Monitor for repeated NetSchedScan application crashes on endpoint systems
• Implement endpoint detection rules for applications experiencing stack buffer overflows
• Configure crash dump analysis to identify patterns consistent with buffer overflow exploitation

Monitoring Recommendations

• Enable Windows Error Reporting to capture crash dumps from NetSchedScan
• Monitor application stability metrics for systems with NetSchedScan installed
• Review security event logs for signs of exploitation attempts or repeated application failures

How to Mitigate CVE-2016-20050

Immediate Actions Required

• Remove or disable NetSchedScan 1.0 from systems where it is not required
• Restrict local access to systems running NetSchedScan to trusted users only
• Consider using alternative network scanning tools that are actively maintained and patched
• Implement application whitelisting to prevent unauthorized use of vulnerable applications

Patch Information

No vendor patch information is currently available for this vulnerability. The Vulncheck Security Advisory provides additional details about the vulnerability status. Organizations should consider discontinuing use of this application in favor of actively supported alternatives.

Workarounds

• Uninstall NetSchedScan 1.0 from production systems
• If removal is not possible, restrict application usage to isolated environments
• Implement host-based security controls to limit user input to the application
• Use network segmentation to contain any potential impact from compromised systems

Since no official patch is available, removal or replacement of the vulnerable software is the recommended mitigation approach.