CVE-2019-25321: FTP Navigator 8.03 RCE Vulnerability

CVE-2019-25321 Overview

FTP Navigator 8.03 contains a critical stack overflow vulnerability (CWE-121) that allows attackers to execute arbitrary code by overwriting Structured Exception Handler (SEH) registers. This classic buffer overflow vulnerability occurs when processing user input in the Custom Command textbox, enabling attackers to achieve code execution on vulnerable systems.

Critical Impact

Successful exploitation allows arbitrary code execution through SEH overwrite, potentially leading to complete system compromise.

Affected Products

• FTP Navigator version 8.03
• FTP Navigator Custom Command functionality
• Windows systems running vulnerable FTP Navigator versions

Discovery Timeline

• 2026-02-12 - CVE CVE-2019-25321 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2019-25321

Vulnerability Analysis

This vulnerability is classified as a Stack-based Buffer Overflow (CWE-121), a memory corruption vulnerability that occurs when a program writes data beyond the boundaries of a pre-allocated fixed-size buffer on the stack. In FTP Navigator 8.03, the vulnerability manifests when handling input through the Custom Command textbox.

The attack requires local access and user interaction, as an attacker must convince a user to paste a malicious payload into the Custom Command field. Once triggered, the overflow corrupts stack memory and overwrites the Structured Exception Handler (SEH) chain, allowing the attacker to redirect program execution to attacker-controlled code.

Proof-of-concept exploits demonstrate the vulnerability by launching the Windows calculator (calc.exe), a common technique to prove arbitrary code execution without causing harm. The existence of multiple public exploits on Exploit-DB #47794 and Exploit-DB #47812 increases the risk of malicious exploitation.

Root Cause

The root cause of this vulnerability is improper bounds checking when processing user-supplied input in the Custom Command textbox. FTP Navigator fails to validate the length of input data before copying it into a fixed-size stack buffer, allowing attackers to overflow the buffer and corrupt adjacent memory structures including the SEH chain.

Attack Vector

The attack vector is local, requiring the attacker to craft a malicious payload string and have it pasted into the Custom Command textbox by a user. The exploitation technique leverages SEH (Structured Exception Handler) overwrite, a well-known Windows exploitation method that bypasses certain stack protection mechanisms.

The attack flow involves:

1. Crafting a payload with specific offsets to reach the SEH pointer
2. Overwriting the SEH handler with an address pointing to attacker-controlled shellcode
3. Triggering an exception to transfer execution to the overwritten handler
4. Executing arbitrary code with the privileges of the FTP Navigator process

For detailed exploitation techniques, refer to the VulnCheck Advisory on FTP Navigator and the public exploits available on Exploit-DB.

Detection Methods for CVE-2019-25321

Indicators of Compromise

• Presence of FTP Navigator version 8.03 installed on systems
• Unusual process spawning from ftpnavigator.exe (e.g., cmd.exe, calc.exe, or powershell.exe)
• Exception handling violations or application crashes in FTP Navigator
• Suspicious large clipboard operations targeting FTP Navigator

Detection Strategies

• Monitor for stack buffer overflow patterns in FTP Navigator process memory
• Deploy application crash monitoring for ftpnavigator.exe with SEH violations
• Implement endpoint detection rules for child process spawning from FTP Navigator
• Use memory integrity monitoring to detect SEH chain corruption

Monitoring Recommendations

• Configure SIEM alerts for unusual activity originating from FTP Navigator processes
• Enable Windows Event Log monitoring for application crashes and exception events
• Deploy SentinelOne endpoint agents to detect and prevent exploitation attempts
• Maintain software inventory to identify systems running vulnerable FTP Navigator versions

How to Mitigate CVE-2019-25321

Immediate Actions Required

• Identify and inventory all systems running FTP Navigator 8.03
• Consider removing or disabling FTP Navigator if not business-critical
• Restrict user access to the Custom Command functionality where possible
• Deploy endpoint protection solutions capable of detecting buffer overflow exploitation

Patch Information

No official patch information is currently available from the vendor. The software appears to be legacy with the vendor website available at Internet Soft Homepage. Organizations should evaluate alternative FTP client solutions with active security maintenance and modern exploit mitigations.

Workarounds

• Migrate to a modern FTP client with active security support and built-in exploit mitigations
• Implement application whitelisting to prevent unauthorized code execution
• Use Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) at the system level
• Restrict FTP Navigator usage to isolated systems or virtual environments
• Train users to avoid pasting content from untrusted sources into application fields

# Configuration example - Enable DEP system-wide on Windows
# Run as Administrator in Command Prompt
bcdedit /set nx AlwaysOn

# Verify DEP status
wmic OS Get DataExecutionPrevention_SupportPolicy