CVE-2025-4978: Netgear DGND3700 Auth Bypass Vulnerability

CVE-2025-4978 Overview

A critical authentication bypass vulnerability has been discovered in the Netgear DGND3700 router firmware version 1.1.00.15_1.00.15NA. This vulnerability affects the Basic Authentication component, specifically within the /BRS_top.html file, allowing remote attackers to bypass authentication mechanisms and gain unauthorized access to the device's administrative interface. The improper authentication flaw (CWE-287) enables unauthenticated network-based attackers to compromise the router without any user interaction.

Critical Impact

Remote attackers can bypass authentication on affected Netgear DGND3700 routers, potentially gaining full administrative control over the device and compromising network security.

Affected Products

• Netgear DGND3700 Firmware version 1.1.00.15_1.00.15NA
• Netgear DGND3700 v2 hardware
• Other Netgear products may also be affected

Discovery Timeline

• May 20, 2025 - CVE-2025-4978 published to NVD
• June 12, 2025 - Last updated in NVD database

Technical Details for CVE-2025-4978

Vulnerability Analysis

This authentication bypass vulnerability resides in the Basic Authentication component of the Netgear DGND3700 router. The vulnerability affects the /BRS_top.html endpoint, which fails to properly validate authentication credentials before granting access to protected resources. Due to this improper authentication implementation, attackers can access administrative functions without providing valid credentials.

The vulnerability is network-accessible and requires no privileges or user interaction to exploit, making it particularly dangerous for internet-exposed devices. Once exploited, attackers can achieve high impact on confidentiality, integrity, and availability of the affected system. The vendor was contacted early about this disclosure, and the exploit details have been publicly disclosed.

Root Cause

The root cause of this vulnerability is improper authentication handling (CWE-287) within the router's web interface. The /BRS_top.html file does not adequately enforce authentication checks, allowing requests to bypass the normal credential verification process. This fundamental flaw in the authentication logic permits unauthorized users to access protected administrative functionality without proper validation of their identity.

Attack Vector

The attack can be initiated remotely over the network. An attacker with network access to the vulnerable router's management interface can exploit this vulnerability by directly accessing the /BRS_top.html endpoint, bypassing the Basic Authentication mechanism entirely. The attack requires no authentication, no privileges, and no user interaction, making it trivially exploitable.

The vulnerability allows attackers to:

• Bypass authentication controls on the router's web interface
• Access administrative configuration pages without credentials
• Potentially modify router settings, DNS configurations, and firewall rules
• Compromise the security of the entire network behind the router

Technical details and proof-of-concept information are available in the GitHub Backdoor Vulnerability Report.

Detection Methods for CVE-2025-4978

Indicators of Compromise

• Unexpected access to /BRS_top.html endpoint without authentication
• Anomalous HTTP requests targeting the router's management interface from external IP addresses
• Unauthorized configuration changes on Netgear DGND3700 devices
• Web server logs showing direct access attempts to the Basic Authentication component

Detection Strategies

• Monitor network traffic for HTTP requests to /BRS_top.html on Netgear DGND3700 devices
• Implement network intrusion detection rules to alert on authentication bypass attempts targeting router management interfaces
• Review router access logs for suspicious unauthenticated access patterns
• Deploy SentinelOne Singularity to detect and respond to network-based attacks targeting IoT and router devices

Monitoring Recommendations

• Enable logging on Netgear DGND3700 devices and forward logs to a centralized SIEM solution
• Monitor for configuration changes on affected routers that occur outside of maintenance windows
• Implement network segmentation to isolate router management interfaces from untrusted networks
• Establish baseline network behavior to detect anomalous access patterns to administrative endpoints

How to Mitigate CVE-2025-4978

Immediate Actions Required

• Restrict access to the router's management interface to trusted internal networks only
• Disable remote management features if not required
• Implement firewall rules to block external access to the router's administrative ports
• Consider replacing end-of-life Netgear DGND3700 devices with supported hardware

Patch Information

At the time of this writing, no official patch from Netgear has been documented in the vulnerability data. Organizations should monitor the Netgear Official Site for security advisories and firmware updates. Given the DGND3700 is an older model, it may be at or approaching end-of-life status, which could limit the availability of security patches. Additional technical details can be found in the VulDB #309639 entry.

Workarounds

• Restrict management interface access by implementing ACLs that permit only specific trusted IP addresses
• Place the router management interface behind a VPN to prevent direct internet exposure
• Use network segmentation to isolate the router from critical network assets
• Consider deploying a Web Application Firewall (WAF) or similar protection in front of the management interface
• If the device cannot be patched or adequately protected, replace it with a newer, supported model

# Example firewall rule to restrict management access (adjust for your environment)
# Block external access to router management port
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP