CVE-2020-10173: Comtrend VR-3033 Auth Bypass Vulnerability

CVE-2020-10173 Overview

CVE-2020-10173 is a command injection vulnerability affecting Comtrend VR-3033 routers running firmware version DE11-416SSG-C01_R02.A2pvI042j1.d26m. The vulnerability exists in the diagnostic pages of the router's web interface, specifically in the ping and traceroute functionality. Authenticated attackers can inject arbitrary shell commands through the pingIpAddress parameter in ping.cgi, potentially leading to complete device compromise.

Critical Impact

Authenticated attackers can execute arbitrary system commands on vulnerable Comtrend VR-3033 routers, enabling full device takeover, network reconnaissance, and lateral movement within the network.

Affected Products

• Comtrend VR-3033 Firmware version DE11-416SSG-C01_R02.A2pvI042j1.d26m
• Comtrend VR-3033 Hardware

Discovery Timeline

• 2020-03-05 - CVE CVE-2020-10173 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-10173

Vulnerability Analysis

This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly known as OS Command Injection. The Comtrend VR-3033 router's web management interface contains multiple diagnostic utilities that fail to properly sanitize user input before passing it to underlying system commands.

The vulnerability is exploitable over the network by an authenticated user with low privileges. No user interaction is required for exploitation. When successfully exploited, attackers can achieve complete compromise of the affected device, including the ability to read sensitive configuration data, modify system settings, and pivot to other network resources.

The high exploitation probability indicated by threat intelligence data suggests this vulnerability is an attractive target for threat actors, particularly given the widespread deployment of consumer and small business routers.

Root Cause

The root cause of this vulnerability is insufficient input validation in the router's diagnostic functionality. The web application accepts user-supplied parameters for network diagnostic tools (ping and traceroute) and passes them directly to shell commands without proper sanitization or escaping of shell metacharacters.

Specifically, the pingIpAddress parameter in ping.cgi is concatenated directly into a system command string, allowing attackers to break out of the intended command context using shell metacharacters such as semicolons (;), backticks (`), pipes (|), or command substitution syntax ($()).

Attack Vector

The attack is network-based and requires authenticated access to the router's web management interface. An attacker with valid credentials (which may be default credentials on many consumer routers) can navigate to the diagnostic pages and submit malicious input containing shell metacharacters.

For example, submitting a value like 192.168.1.1; cat /etc/passwd or $(whoami) in the pingIpAddress field would cause the router to execute the injected commands with the privileges of the web server process, typically running as root on embedded devices.

The attack can be leveraged to establish persistent access, exfiltrate sensitive data such as wireless credentials and configuration files, or use the compromised device as a pivot point for further network attacks.

Detection Methods for CVE-2020-10173

Indicators of Compromise

• Unusual HTTP POST requests to /ping.cgi or /traceroute.cgi containing shell metacharacters (;, |, $(), backticks)
• Unexpected outbound connections from the router to external IP addresses
• Modified router configuration files or unexpected scheduled tasks (cron jobs)
• Presence of unfamiliar files or scripts in writable directories on the router filesystem

Detection Strategies

• Monitor web server logs on network devices for requests containing suspicious characters in diagnostic parameters
• Implement network monitoring to detect anomalous traffic patterns from router management interfaces
• Deploy intrusion detection rules to identify command injection patterns in HTTP traffic to router diagnostic endpoints
• Review router configurations periodically for unauthorized changes or backdoor accounts

Monitoring Recommendations

• Enable logging on the Comtrend VR-3033 web interface and forward logs to a centralized SIEM for analysis
• Implement network segmentation to isolate router management interfaces from untrusted networks
• Monitor for unusual DNS queries or network connections originating from router IP addresses
• Set up alerts for multiple failed authentication attempts followed by successful logins to router management interfaces

How to Mitigate CVE-2020-10173

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Change default credentials immediately and implement strong, unique passwords
• Disable remote management access if not required
• Place router management interfaces on a separate VLAN with strict access controls
• Consider replacing affected devices if no firmware update is available

Patch Information

No vendor advisory or official patch information is currently available for this vulnerability. Organizations should contact Comtrend directly for guidance on firmware updates or consider replacing affected devices with supported alternatives.

Additional technical details are available in the Exploit-DB entry #48142.

Workarounds

• Implement firewall rules to block access to the web management interface from untrusted networks
• Use a VPN for remote management access instead of exposing the web interface directly
• Disable the diagnostic functionality (ping/traceroute pages) if not required for operations
• Deploy a web application firewall (WAF) or reverse proxy in front of the management interface to filter malicious input patterns
• Monitor and audit all administrative access to the device