CVE-2019-25660: LanHelper DoS Vulnerability

CVE-2019-25660 Overview

CVE-2019-25660 is a local buffer overflow vulnerability affecting LanHelper version 1.74, a network management utility. The vulnerability exists in the Form Send Message feature, where improper handling of user-supplied input allows attackers to trigger a denial of service condition by providing excessively long input strings. Specifically, pasting approximately 6000 bytes of data into the Message text field causes the application to crash.

This vulnerability is classified as CWE-787 (Out-of-bounds Write), which occurs when software writes data past the end of a buffer, potentially leading to memory corruption and application instability.

Critical Impact

Local attackers can crash the LanHelper application by exploiting the buffer overflow in the Form Send Message feature, causing denial of service to network management operations.

Affected Products

• LanHelper 1.74

Discovery Timeline

• 2026-04-05 - CVE CVE-2019-25660 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2019-25660

Vulnerability Analysis

The vulnerability resides in LanHelper's Form Send Message functionality, which fails to properly validate the length of user input before copying it into a fixed-size buffer. When a user pastes approximately 6000 bytes of data into the Message text field, the application attempts to store this data in a buffer that cannot accommodate such large inputs. This results in memory being overwritten beyond the allocated buffer boundaries.

The local attack vector means an attacker must have access to the system where LanHelper is installed to exploit this vulnerability. While this limits the attack surface compared to network-exploitable vulnerabilities, it still poses a risk in shared computing environments or when combined with other attack vectors that provide local access.

Root Cause

The root cause of this vulnerability is improper input validation in the message handling component of LanHelper. The application does not enforce adequate length restrictions on user-supplied data in the Message text field within the Form Send Message feature. When input exceeding the buffer capacity is provided, the application performs an unbounded copy operation, writing data past the allocated memory region and triggering an out-of-bounds write condition (CWE-787).

Attack Vector

The attack is executed locally through the LanHelper application interface. An attacker with access to the application can navigate to the Form Send Message feature and paste a crafted payload of approximately 6000 bytes into the Message text field. Upon processing this oversized input, the buffer overflow occurs, causing the application to crash. The attack requires no special privileges and no user interaction beyond the attacker's own actions.

The exploitation technique is documented in Exploit-DB #46295, which provides details on triggering the denial of service condition through the buffer overflow.

Detection Methods for CVE-2019-25660

Indicators of Compromise

• Application crash events for LanHelper (LanHelper.exe) with access violation or memory corruption errors
• Unexpected termination of network management services associated with LanHelper
• Windows Event Log entries indicating application faults in LanHelper processes
• Memory dump files generated from LanHelper crashes showing buffer overflow patterns

Detection Strategies

• Monitor for repeated crashes of LanHelper application processes that may indicate exploitation attempts
• Implement application whitelisting and integrity monitoring to detect unauthorized modifications to LanHelper
• Use endpoint detection and response (EDR) solutions to identify suspicious memory access patterns in LanHelper processes
• Review system logs for crash reports or Dr. Watson entries related to LanHelper

Monitoring Recommendations

• Configure crash dump collection for LanHelper to enable forensic analysis of potential exploitation attempts
• Implement file integrity monitoring on LanHelper installation directories
• Monitor process behavior for abnormal memory allocation patterns associated with LanHelper
• Enable Windows Error Reporting to capture detailed crash information for security analysis

How to Mitigate CVE-2019-25660

Immediate Actions Required

• Restrict access to systems running LanHelper 1.74 to trusted users only
• Consider discontinuing use of LanHelper 1.74 if an updated version addressing this vulnerability is not available
• Implement network segmentation to limit the impact of potential denial of service conditions
• Deploy endpoint protection solutions capable of detecting buffer overflow exploitation attempts

Patch Information

No vendor patch information is currently available for this vulnerability. The vendor, Hainsoft, should be contacted directly via their official website for information about security updates or newer versions that may address this issue. Additional technical details are available in the VulnCheck Denial of Service Advisory.

Workarounds

• Restrict physical and remote access to systems running the vulnerable LanHelper version
• Implement least privilege principles to limit which users can access the LanHelper application
• Consider alternative network management tools that do not have known buffer overflow vulnerabilities
• Monitor for application crashes and investigate any unexpected LanHelper terminations as potential security incidents
• If continued use is necessary, isolate systems running LanHelper from sensitive network segments

# Example: Restrict LanHelper execution to specific users (Windows)
# Use NTFS permissions to limit access to LanHelper.exe
icacls "C:\Program Files\LanHelper\LanHelper.exe" /inheritance:r /grant:r Administrators:RX