CVE-2020-37220: Huawei HG630 V2 Auth Bypass Vulnerability

CVE-2020-37220 Overview

CVE-2020-37220 is an authentication bypass vulnerability in the Huawei HG630 V2 router. The device exposes the /api/system/deviceinfo endpoint without requiring authentication. An unauthenticated remote attacker can query this endpoint and extract the SerialNumber field from the response. The last 8 characters of the serial number function as the default administrator password, allowing the attacker to log in with administrative privileges. The flaw is classified under CWE-798: Use of Hard-coded Credentials.

Critical Impact

Unauthenticated network attackers can derive valid administrator credentials directly from the router and gain full administrative control over the device.

Affected Products

• Huawei HG630 V2 Router
• Huawei HG630 V2 Router firmware exposing the /api/system/deviceinfo endpoint
• Deployments using factory-default administrator credentials

Discovery Timeline

• 2026-05-13 - CVE-2020-37220 published to the National Vulnerability Database (NVD)
• 2026-05-13 - Last updated in the NVD database

Technical Details for CVE-2020-37220

Vulnerability Analysis

The Huawei HG630 V2 router exposes a web API endpoint at /api/system/deviceinfo that returns device metadata without enforcing authentication. The response payload contains a SerialNumber field that uniquely identifies the device. The manufacturer's default administrative password is derived deterministically from the serial number, specifically the last 8 characters. This design ties a publicly readable device attribute directly to a credential, breaking the confidentiality assumption of the authentication system.

An attacker performs a single HTTP GET request to retrieve the serial number, computes the default password, and authenticates to the web management interface. No exploit chain or memory corruption primitive is required. The combination of an unauthenticated information disclosure and hard-coded credential derivation produces a complete authentication bypass.

Details of the issue are documented in the VulnCheck Advisory and the public proof of concept published as Exploit-DB #48310.

Root Cause

The root cause is twofold. First, the /api/system/deviceinfo endpoint lacks authentication and authorization controls. Second, the default administrator credential is algorithmically derived from the device serial number rather than being randomized or required to be changed at first login. This is a textbook instance of CWE-798: Use of Hard-coded Credentials.

Attack Vector

The attack is network-based and requires no authentication, no user interaction, and no privileges. An attacker with network reachability to the router's management interface issues an HTTP GET request to /api/system/deviceinfo, parses the JSON response, extracts the SerialNumber value, takes the trailing 8 characters, and submits them as the password to the login interface. Devices exposed to the internet or to untrusted local network segments are at immediate risk.

No verified exploitation code is reproduced here. Refer to Exploit-DB #48310 for the published proof of concept.

Detection Methods for CVE-2020-37220

Indicators of Compromise

• Unauthenticated HTTP GET requests to /api/system/deviceinfo originating from external or unexpected internal sources
• Successful administrative logins to the router web interface immediately following a request to the device info endpoint
• Configuration changes on the router (DNS, firewall rules, port forwarding, firmware updates) initiated from unfamiliar source addresses
• New or unexpected administrative sessions in the router event log

Detection Strategies

• Inspect router and upstream web traffic logs for requests to /api/system/deviceinfo that are not initiated by legitimate management workflows
• Correlate device info endpoint access with subsequent login events to identify the disclosure-then-login pattern
• Alert on administrative logins occurring outside approved maintenance windows or from unapproved IP ranges

Monitoring Recommendations

• Forward router syslog data to a central logging or SIEM platform for retention and analysis
• Monitor for configuration drift on customer premises equipment (CPE) using periodic configuration snapshots
• Track outbound DNS and traffic anomalies from the router that could indicate post-compromise redirection or tunneling

How to Mitigate CVE-2020-37220

Immediate Actions Required

• Change the router administrator password to a strong, unique value that is not derived from the serial number
• Restrict access to the router web management interface to trusted internal addresses and disable remote (WAN-side) management
• Audit router configuration for unauthorized changes to DNS, DHCP, firewall, and port forwarding settings
• Replace the device if the vendor no longer issues firmware updates for the HG630 V2 platform

Patch Information

No vendor patch is referenced in the available advisory data. Operators should consult Huawei support channels for firmware availability for the HG630 V2 and review the VulnCheck Advisory for the latest remediation guidance. Where firmware updates are not available, compensating controls and device replacement are the recommended path.

Workarounds

• Block external access to the management interface at the upstream firewall or ISP boundary
• Place the router behind a network segment that restricts management traffic to a dedicated administrative VLAN
• Disable any HTTP/HTTPS management services that are not required for operations
• Rotate the administrator password and verify that the new value bears no relation to the device serial number

# Example: restrict access to the router management interface using iptables on an upstream gateway
iptables -A FORWARD -d <router_mgmt_ip> -p tcp --dport 80 -s <trusted_admin_subnet> -j ACCEPT
iptables -A FORWARD -d <router_mgmt_ip> -p tcp --dport 443 -s <trusted_admin_subnet> -j ACCEPT
iptables -A FORWARD -d <router_mgmt_ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <router_mgmt_ip> -p tcp --dport 443 -j DROP