CVE-2019-25329: FTP Navigator DoS Vulnerability

CVE-2019-25329 Overview

FTP Navigator 8.03 contains a denial of service vulnerability that allows attackers to crash the application by overwriting Structured Exception Handler (SEH) with malicious input. This stack-based buffer overflow vulnerability (CWE-121) can be triggered when an attacker crafts a specific payload and pastes it into the custom command input field, causing the application to crash.

Critical Impact

Local attackers can cause application crashes and denial of service by exploiting improper input validation in the custom command functionality, potentially disrupting FTP file transfer operations.

Affected Products

• FTP Navigator version 8.03
• Windows-based FTP client installations using vulnerable version
• Systems where users interact with untrusted input in custom command fields

Discovery Timeline

• 2026-02-12 - CVE CVE-2019-25329 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2019-25329

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), which occurs when the application fails to properly validate the length of user-supplied input before copying it to a fixed-size stack buffer. The vulnerable component is the custom command input handler in FTP Navigator 8.03.

The attack requires local access and user interaction, meaning an attacker would need to convince a user to paste malicious input into the application or have direct access to the system. When exploited, the vulnerability overwrites the Structured Exception Handler (SEH) chain, which Windows uses to handle runtime exceptions. By corrupting the SEH chain, the attacker can cause the application to crash when an exception is raised.

Root Cause

The root cause of this vulnerability lies in inadequate bounds checking within the custom command input processing routine. FTP Navigator 8.03 allocates a fixed-size buffer for storing user input but does not validate that the input length falls within acceptable limits before performing the copy operation. This allows an attacker to supply input exceeding the buffer's capacity, resulting in adjacent stack memory—including the SEH records—being overwritten.

Attack Vector

The attack vector is local, requiring either physical access to the system or social engineering to convince a user to paste the malicious payload. The exploitation technique involves crafting a specifically structured input string that overflows the stack buffer and corrupts the SEH chain.

According to the Exploit-DB #47794, attackers can generate a payload consisting of 4108 'A' characters followed by 4 'B' characters and 40 'C' characters. When this payload is pasted into the custom command input field, the overflow occurs and the SEH is overwritten with the attacker-controlled values, causing the program to crash when an exception handler is invoked.

The 'A' characters fill the buffer up to and past its boundary, the 'B' characters overwrite the SEH handler pointer, and the 'C' characters provide additional padding. This demonstrates a classic SEH-based overflow pattern commonly seen in Windows application vulnerabilities.

Detection Methods for CVE-2019-25329

Indicators of Compromise

• Unexpected crashes of the FTP Navigator application, particularly when using custom command functionality
• Application crash logs showing access violations or exception handling errors
• Presence of large strings or unusual patterns in clipboard history related to FTP Navigator usage
• Windows Event Viewer entries indicating application faults in ftpnav.exe or similar FTP Navigator binaries

Detection Strategies

• Monitor for unusual application crashes in FTP Navigator with stack corruption signatures
• Implement application whitelisting to prevent execution of vulnerable versions of FTP Navigator
• Use endpoint detection tools to identify SEH overwrite patterns in running processes
• Deploy behavioral analysis to detect buffer overflow exploitation attempts

Monitoring Recommendations

• Enable Windows Error Reporting to capture crash dumps for forensic analysis
• Monitor process stability metrics for FTP Navigator installations across the environment
• Implement logging for clipboard operations on sensitive systems where FTP Navigator is deployed
• Review application event logs for repeated crash patterns that may indicate exploitation attempts

How to Mitigate CVE-2019-25329

Immediate Actions Required

• Evaluate the necessity of FTP Navigator 8.03 in your environment and consider migrating to alternative, actively maintained FTP clients
• Restrict access to systems running vulnerable versions to trusted users only
• Implement application control policies to prevent unauthorized use of the affected software
• Educate users about the risks of pasting untrusted content into application input fields

Patch Information

No vendor patch information is currently available for this vulnerability. The vendor, Internet Soft, has not released an updated version addressing this issue. Organizations should consider the following alternatives:

• Migrate to actively maintained FTP client software with better security practices
• Review the VulnCheck Advisory on FTP Navigator for the latest information on this vulnerability
• Contact the vendor through Internet Soft Home Page for potential updates or security guidance

Workarounds

• Avoid using the custom command feature in FTP Navigator 8.03 until a patch is available
• Implement input validation at the network or endpoint level to filter potentially malicious clipboard content
• Consider running FTP Navigator in a sandboxed environment to limit the impact of exploitation
• Deploy Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) at the system level to make SEH exploitation more difficult

Organizations should prioritize migrating away from FTP Navigator 8.03 to a more secure and actively maintained FTP client solution, as this application appears to be legacy software without ongoing security support.