CVE-2025-4978: Netgear DGND3700 Auth Bypass Vulnerability

CVE-2025-4978 Overview

CVE-2025-4978 is an improper authentication vulnerability [CWE-287] affecting the Netgear DGND3700 wireless router running firmware version 1.1.00.15_1.00.15NA. The flaw resides in the Basic Authentication component, specifically within the /BRS_top.html page. Attackers can bypass authentication remotely without user interaction, gaining access to administrative router functions. Public exploitation details have been disclosed, and additional Netgear product variants may share the same defect.

Critical Impact

Remote attackers can bypass Basic Authentication on affected Netgear DGND3700 routers, achieving unauthorized administrative access over the network without credentials or user interaction.

Affected Products

• Netgear DGND3700 firmware 1.1.00.15_1.00.15NA
• Netgear DGND3700 v2 hardware
• Other Netgear models may be affected per vendor disclosure

Discovery Timeline

• 2025-05-20 - CVE-2025-4978 published to NVD
• 2025-06-12 - Last updated in NVD database

Technical Details for CVE-2025-4978

Vulnerability Analysis

The vulnerability allows unauthenticated remote attackers to bypass the router's Basic Authentication mechanism by interacting with the /BRS_top.html endpoint. The endpoint fails to enforce session validation before processing privileged requests. An attacker on the network path to the device can manipulate the request flow to access protected administrative functionality without supplying valid credentials.

Successful exploitation grants attackers the ability to view or modify router configuration, including wireless settings, DNS configuration, firewall rules, and credential stores. Attackers can pivot from a compromised router to intercept LAN traffic, redirect DNS queries, or stage further attacks against connected hosts. Public documentation of the backdoor behavior is available in the GitHub Backdoor Documentation.

Root Cause

The root cause is improper authentication enforcement [CWE-287] within the web administration interface. The /BRS_top.html resource — part of the Basic Setup workflow — does not validate an authenticated session before exposing functionality intended for authorized administrators. This logic flaw enables direct access to privileged operations through a documented backdoor-style path.

Attack Vector

The attack vector is network-based and requires no privileges or user interaction. An attacker reaches the router's HTTP administration interface — typically port 80 on the LAN, or the WAN if remote management is enabled — and issues crafted requests against /BRS_top.html. The exploit has been publicly disclosed, increasing the risk of opportunistic scanning and weaponization. Refer to VulDB #309639 for additional technical context.

Detection Methods for CVE-2025-4978

Indicators of Compromise

• Unexpected HTTP requests to /BRS_top.html from external or untrusted internal hosts
• Unauthorized changes to router DNS, wireless, or firewall settings on DGND3700 devices
• New or modified administrative accounts on the router web interface
• Outbound traffic from LAN clients redirected through unfamiliar DNS servers

Detection Strategies

• Monitor HTTP access logs from network management appliances for requests to /BRS_top.html on DGND3700 IP addresses
• Inspect router syslog output for configuration changes occurring outside of authorized maintenance windows
• Apply network IDS signatures matching unauthenticated GET or POST requests to the vulnerable endpoint

Monitoring Recommendations

• Forward router and gateway syslog data to a centralized SIEM for correlation against administrative change baselines
• Alert on changes to DNS resolver settings advertised by DHCP from affected routers
• Track inbound connections to TCP/80 and TCP/443 on devices exposing remote management

How to Mitigate CVE-2025-4978

Immediate Actions Required

• Disable remote (WAN-side) management on affected DGND3700 routers immediately
• Restrict LAN access to the router administration interface to a dedicated management VLAN or specific trusted hosts
• Audit router configuration for unauthorized changes to DNS, firewall, and wireless settings
• Plan replacement of the DGND3700, which is an end-of-life product unlikely to receive firmware updates

Patch Information

No vendor patch is referenced in the NVD entry or external advisories at the time of publication. The Netgear DGND3700 is a legacy device, and prior end-of-life products in this family have not historically received security firmware updates. Check the Netgear Official Website for any vendor advisory before relying on configuration-based mitigations alone.

Workarounds

• Replace the DGND3700 with a currently supported router model that receives security updates
• Place the affected device behind an upstream firewall and block external access to TCP/80 and TCP/443
• Disable HTTP administration entirely if the device supports a CLI-only management mode
• Segment IoT and legacy devices onto an isolated network to limit pivot opportunities if the router is compromised