CVE-2025-3762: Pcman FTP Server Buffer Overflow Flaw

CVE-2025-3762 Overview

CVE-2025-3762 is a buffer overflow vulnerability in PCMan FTP Server version 2.0.7. The flaw resides in the MPUT command handler, where unvalidated input enables memory corruption. Attackers can trigger the condition remotely without authentication. Public exploit details have been disclosed, increasing the risk of opportunistic exploitation against exposed FTP services. The weakness is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer).

Critical Impact
Remote attackers can send crafted MPUT commands to corrupt memory in PCMan FTP Server 2.0.7, leading to service disruption and potential arbitrary code execution.

Affected Products

PCMan FTP Server 2.0.7
Component: MPUT Command Handler
Vendor: PCMan

Discovery Timeline

2025-04-17 - CVE-2025-3762 published to NVD
2025-05-12 - Last updated in NVD database

Technical Details for CVE-2025-3762

Vulnerability Analysis

The vulnerability affects the MPUT command handler in PCMan FTP Server 2.0.7. The handler fails to enforce size limits on attacker-supplied input before copying it into a fixed-size buffer. This results in memory corruption when oversized arguments are submitted through a connected FTP session. Because PCMan FTP Server runs as a network-facing service, attackers can reach the vulnerable code path remotely. The publicly disclosed exploit lowers the barrier for adversaries to weaponize the issue against exposed deployments. EPSS data indicates a probability of 0.479% with a percentile of 65.169, reflecting moderate observed interest.

Root Cause

The root cause is improper bounds checking in the MPUT command processing routine. The handler accepts client-supplied data and writes it into a stack or heap buffer without verifying that the input fits within allocated memory. This violates safe memory handling practices captured by [CWE-119]. The defect originates in legacy C/C++ string handling patterns that rely on length-unaware copy operations.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker establishes an FTP session with a vulnerable PCMan FTP Server 2.0.7 instance and issues a crafted MPUT command containing an oversized argument. The malformed input overruns the destination buffer, corrupting adjacent memory. Depending on stack layout and protections, the corruption can crash the service or be leveraged for code execution. Refer to the Fitoxs Exploit Document and the VulDB entry #305396 for technical specifics.

Detection Methods for CVE-2025-3762

Indicators of Compromise

Unexpected crashes or restarts of the PCMan.exe FTP service process
FTP session logs containing MPUT commands with abnormally long arguments
Inbound TCP connections to port 21 originating from untrusted sources followed by service termination
New or unexplained child processes spawned by the PCMan FTP Server binary

Detection Strategies

Inspect FTP protocol traffic for MPUT commands exceeding reasonable filename lengths
Correlate FTP service crashes with preceding network activity from external sources
Apply network intrusion detection signatures targeting oversized FTP command arguments
Enable application crash reporting on hosts running PCMan FTP Server to capture exploitation attempts

Monitoring Recommendations

Log all FTP control channel commands and argument lengths for retrospective analysis
Alert on repeated FTP service restarts within short time windows
Monitor host-based telemetry for anomalous process behavior associated with the FTP server binary
Track external connections to TCP port 21 on systems not designated as production FTP servers

How to Mitigate CVE-2025-3762

Immediate Actions Required

Restrict network access to PCMan FTP Server 2.0.7 instances using firewall rules limiting inbound TCP port 21
Decommission PCMan FTP Server 2.0.7 in production environments and migrate to a maintained FTP solution
Audit perimeter exposure to identify any internet-reachable PCMan FTP Server installations
Review FTP logs for prior MPUT activity from untrusted sources

Patch Information

No vendor patch is referenced in the published advisory for CVE-2025-3762. PCMan FTP Server is legacy software with limited active maintenance. Organizations should plan migration to a supported FTP server product rather than relying on a fix.

Workarounds

Disable the PCMan FTP Server service if it is not required for business operations
Place the FTP service behind a VPN or zero-trust gateway to remove direct internet exposure
Apply network segmentation to isolate the FTP host from sensitive internal assets
Configure host firewalls to allow FTP connections only from explicitly trusted IP ranges

bash

# Example Windows firewall rule restricting inbound FTP to trusted sources
netsh advfirewall firewall add rule name="Restrict PCMan FTP" ^
  dir=in action=block protocol=TCP localport=21

netsh advfirewall firewall add rule name="Allow Trusted FTP" ^
  dir=in action=allow protocol=TCP localport=21 ^
  remoteip=10.0.0.0/24