CVE-2019-25466: Easy File Sharing 7.2 Buffer Overflow

CVE-2019-25466 Overview

Easy File Sharing Web Server 7.2 contains a local structured exception handling (SEH) buffer overflow vulnerability that allows local attackers to execute arbitrary code by creating a malicious username. Attackers can craft a username with a payload containing 4059 bytes of padding followed by a nseh value and seh pointer to trigger the overflow when adding a new user account.

Critical Impact

Local attackers can achieve arbitrary code execution on vulnerable systems by exploiting the SEH-based buffer overflow through malicious username creation, potentially leading to complete system compromise.

Affected Products

• Easy File Sharing Web Server 7.2

Discovery Timeline

• 2026-03-11 - CVE CVE-2019-25466 published to NVD
• 2026-03-12 - Last updated in NVD database

Technical Details for CVE-2019-25466

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write), manifesting as a structured exception handling (SEH) based buffer overflow within Easy File Sharing Web Server 7.2. The flaw occurs during the user account creation process, where insufficient bounds checking on the username field allows attackers to overflow a buffer and corrupt the exception handler chain.

SEH-based exploits take advantage of Windows' exception handling mechanism. When an exception occurs, Windows walks the exception handler chain to find an appropriate handler. By overwriting the SEH pointer with a controlled value, an attacker can redirect program execution to arbitrary code when an exception is triggered.

Root Cause

The vulnerability stems from improper input validation when processing username data during account creation. The application fails to adequately validate the length of user-supplied input before copying it into a fixed-size buffer, resulting in an out-of-bounds write condition. This allows an attacker to overwrite adjacent memory, including the structured exception handler records on the stack.

Attack Vector

The attack requires local access to the system running Easy File Sharing Web Server 7.2. An attacker must be able to interact with the application's user account creation functionality. By supplying a specially crafted username containing 4059 bytes of padding followed by carefully calculated nseh and seh pointer values, the attacker can overwrite the exception handler chain. When an exception is subsequently triggered, execution flow is redirected to attacker-controlled code.

The attack leverages the predictable structure of SEH records on the Windows stack:

1. The attacker fills the buffer with padding bytes until reaching the SEH record
2. The Next SEH (nseh) field is overwritten with a short jump instruction
3. The SEH handler pointer is overwritten with an address pointing to a POP POP RET instruction sequence
4. When the exception handler is invoked, execution jumps to the attacker's shellcode

Technical details and proof-of-concept code are available in the Exploit-DB #47411 and VulnCheck Advisory references.

Detection Methods for CVE-2019-25466

Indicators of Compromise

• Presence of unusually long usernames (exceeding 4000 characters) in application logs or configuration files
• Application crashes or unexpected termination of Easy File Sharing Web Server service
• Evidence of post-exploitation activity following application crashes
• Anomalous entries in Windows Event Logs indicating application exceptions

Detection Strategies

• Monitor for process crashes and exception events associated with Easy File Sharing Web Server
• Implement endpoint detection rules that alert on SEH exploitation patterns
• Configure file integrity monitoring on Easy File Sharing Web Server configuration and user data files
• Deploy behavior-based detection to identify code execution following buffer overflow patterns

Monitoring Recommendations

• Enable detailed application logging to capture user creation attempts and associated input lengths
• Configure Windows Event Forwarding to centralize exception and crash events
• Implement process monitoring to detect suspicious child processes spawned from the Easy File Sharing Web Server process
• Review authentication logs for anomalous user account creation patterns

How to Mitigate CVE-2019-25466

Immediate Actions Required

• Discontinue use of Easy File Sharing Web Server 7.2 if possible and migrate to a supported, actively maintained alternative
• Restrict local access to systems running the vulnerable application to trusted users only
• Implement application whitelisting to prevent execution of unauthorized code
• Deploy endpoint protection solutions with exploit mitigation capabilities

Patch Information

No vendor patch information is currently available in the CVE data. Users should consider migrating to alternative file sharing solutions that are actively maintained and receive security updates. For additional technical details, refer to the VulnCheck Advisory.

Workarounds

• Limit physical and remote access to systems running Easy File Sharing Web Server to essential personnel only
• Enable Windows Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) which may provide partial mitigation against exploitation
• Consider running the application in a sandboxed or isolated environment to limit the impact of successful exploitation
• Implement network segmentation to isolate systems running the vulnerable application from critical infrastructure

To enable enhanced Windows exploit mitigations, administrators can configure the following settings:

# Enable DEP for all programs
Set-ProcessMitigation -System -Enable DEP

# Verify ASLR is enabled system-wide
Get-ProcessMitigation -System | Select-Object -ExpandProperty ASLR