CVE-2025-51381: KCM3100 Authentication Bypass Vulnerability

CVE-2025-51381 Overview

CVE-2025-51381 is an authentication bypass vulnerability affecting KCM3100 Ver1.4.2 and earlier. An attacker on the same local area network (LAN) as the affected device can bypass authentication controls and gain unauthorized access to product functions. The flaw is classified under CWE-288: Authentication Bypass Using an Alternate Path or Channel. Japan's JPCERT/CC coordinated the disclosure, and JCOM published a customer notice describing remediation steps.

Critical Impact
Attackers within the LAN can bypass authentication on KCM3100 devices running Ver1.4.2 or earlier, compromising confidentiality, integrity, and availability of the product.

Affected Products

KCM3100 Ver1.4.2
KCM3100 versions prior to Ver1.4.2
Devices distributed through JCOM service deployments

Discovery Timeline

2025-06-18 - CVE-2025-51381 published to the National Vulnerability Database (NVD)
2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-51381

Vulnerability Analysis

The KCM3100 device exposes services on the LAN that fail to properly enforce authentication. An attacker with network access to the device can issue requests that the product processes without verifying the requester's identity. The flaw aligns with CWE-288, where an alternate path or channel allows bypass of the intended authentication checks.

Because exploitation occurs over the network without user interaction, an attacker on the LAN can interact with the device as if authenticated. Successful exploitation impacts confidentiality, integrity, and availability of the device. The vulnerability does not require prior credentials, which lowers the operational bar for adjacent attackers who have already gained foothold on the local network.

Root Cause

The root cause is insufficient enforcement of authentication on one or more LAN-facing interfaces of KCM3100 firmware up to Ver1.4.2. The product accepts privileged requests without validating session state or credentials. Vendor advisories from JVN and JCOM confirm the issue and provide remediation guidance.

Attack Vector

The attack vector is network-based but constrained to the LAN segment hosting the device. An adversary who controls or compromises any LAN-connected host, such as a Wi-Fi client or another IoT device, can reach the KCM3100 management plane. From there, the attacker issues unauthenticated requests that the device honors. No user interaction or credentials are required to complete the bypass.

No public proof-of-concept exploit has been published. See the JVN advisory for vendor-provided technical details.

Detection Methods for CVE-2025-51381

Indicators of Compromise

Unexpected configuration changes on KCM3100 devices, including modified service settings or new administrative entries
Administrative or privileged HTTP requests originating from non-administrative LAN hosts
Connections to the device management interface from endpoints that do not belong to the network operations team

Detection Strategies

Monitor LAN traffic to the KCM3100 management interface and alert on requests from unexpected source addresses
Compare device firmware versions across the fleet against the fixed release published by the vendor
Correlate device configuration change events with the originating client to identify unauthenticated administrative activity

Monitoring Recommendations

Enable logging on the KCM3100 device and forward logs to a centralized SIEM or log platform for retention and review
Baseline normal management traffic patterns and alert on deviations such as off-hours administrative access
Track repeated requests to authentication endpoints that complete without a preceding credential exchange

How to Mitigate CVE-2025-51381

Immediate Actions Required

Inventory all KCM3100 devices and identify any running Ver1.4.2 or earlier firmware
Apply the firmware update referenced in the JCOM notice as soon as it is available for the deployment
Restrict LAN access to the device management interface to a dedicated management VLAN or trusted hosts
Rotate any credentials and configuration secrets stored on devices that may have been exposed

Patch Information

Review the JVN Security Advisory and the JCOM Notice #93847 for vendor-supplied firmware updates and remediation guidance. Apply the fixed firmware version specified by the vendor to all affected KCM3100 units.

Workarounds

Segment the device onto an isolated VLAN that excludes general user endpoints and IoT devices
Block management ports at the LAN switch or firewall for all hosts except a designated administrative workstation
Disable Wi-Fi access to network segments hosting the device until the firmware update is applied

bash

# Example: restrict LAN access to the KCM3100 management interface
# Replace 192.0.2.10 with the device IP and 192.0.2.20 with the admin host IP
iptables -A FORWARD -d 192.0.2.10 -s 192.0.2.20 -j ACCEPT
iptables -A FORWARD -d 192.0.2.10 -j DROP