CVE-2021-47820: Ubee EVW327 CSRF Vulnerability

CVE-2021-47820 Overview

CVE-2021-47820 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the Ubee EVW327 router. This vulnerability allows attackers to craft malicious webpages that automatically submit forms to change the router's remote access settings to port 8080 without the user's knowledge or consent. When a victim visits the attacker's malicious page while authenticated to their router, the CSRF attack executes automatically, enabling remote access to the device.

Critical Impact

Successful exploitation enables unauthorized remote access to the router's management interface, potentially allowing attackers to modify network configurations, intercept traffic, or use the compromised device as a pivot point for further attacks.

Affected Products

• Ubee EVW327 Router

Discovery Timeline

• 2026-01-16 - CVE CVE-2021-47820 published to NVD
• 2026-01-16 - Last updated in NVD database

Technical Details for CVE-2021-47820

Vulnerability Analysis

This vulnerability is classified under CWE-352 (Cross-Site Request Forgery), which occurs when web applications do not adequately verify that requests originate from legitimate user actions. In the case of the Ubee EVW327, the router's administrative interface fails to implement proper CSRF protections when processing requests to modify remote access settings.

The attack requires user interaction—specifically, the victim must visit a malicious webpage while having an active authenticated session with their router. Once triggered, the attack silently submits a request that enables remote management on port 8080, giving the attacker external access to the router's administrative functions.

Root Cause

The root cause of this vulnerability is the absence of anti-CSRF tokens or other request validation mechanisms in the Ubee EVW327's web management interface. The router accepts configuration changes based solely on the presence of valid session cookies, without verifying that the request originated from a legitimate form submission within the administrative interface. This allows attackers to forge requests that appear to come from authenticated users.

Attack Vector

The attack is network-based and requires user interaction. An attacker creates a malicious webpage containing a hidden form that targets the Ubee EVW327's remote access configuration endpoint. When an authenticated user visits this page, the form automatically submits—leveraging the user's existing session cookies—to enable remote access on port 8080. The attacker can then access the router's management interface from the internet.

The malicious webpage typically contains an auto-submitting HTML form with pre-configured values to enable remote access. When loaded in the victim's browser, JavaScript or an onload event triggers form submission to the router's configuration endpoint. Since the browser automatically includes session cookies with the request, the router processes it as a legitimate configuration change.

Technical details and proof-of-concept information can be found in the Exploit-DB entry #49920 and the Vulncheck Advisory.

Detection Methods for CVE-2021-47820

Indicators of Compromise

• Unexpected changes to router remote access settings, particularly enabling remote management on port 8080
• Router management interface accessible from external networks when it should be internal-only
• Browser history showing visits to suspicious or unknown websites prior to configuration changes
• Unusual outbound connections originating from the router's management port

Detection Strategies

• Monitor router configuration changes for unauthorized modifications to remote access settings
• Implement network monitoring to detect external access attempts to router management ports (especially port 8080)
• Review web server logs on the router for configuration change requests originating from unexpected referrer URLs
• Deploy network intrusion detection rules to identify CSRF attack patterns targeting router endpoints

Monitoring Recommendations

• Regularly audit router configurations to verify remote access settings remain as intended
• Set up alerts for any configuration changes to the Ubee EVW327 management interface
• Monitor for external connection attempts to the router's management port from untrusted IP addresses
• Implement logging for all administrative actions on network infrastructure devices

How to Mitigate CVE-2021-47820

Immediate Actions Required

• Disable remote management access on the Ubee EVW327 if not explicitly required
• Ensure router administrative sessions are logged out when not in use
• Use a separate browser or incognito mode when accessing router administration to prevent session-based attacks
• Verify current remote access settings have not been modified without authorization

Patch Information

No vendor patch information is currently available for this vulnerability. Users should check with Ubee Interactive for firmware updates that may address this CSRF vulnerability. Additional technical details are available in the Vulncheck Advisory.

Workarounds

• Disable remote management entirely if it is not required for network operations
• Place the router behind an additional firewall that blocks external access to management ports
• Change the default administrative credentials to strong, unique passwords
• Log out of the router administrative interface immediately after making changes to minimize the session exposure window

# Verify remote access is disabled (example verification steps)
# Check router configuration page for remote management settings
# Ensure "Remote Management" or "Remote Access" is set to DISABLED
# Verify no firewall rules are allowing external access to port 8080
# Consider blocking port 8080 at the network perimeter as additional protection