CVE-2021-20122 in Wi-FI Hub
Summary
by MITRE • 10/11/2021
The Telus Wi-Fi Hub (PRV65B444A-S-TS) with firmware version 3.00.20 is affected by an authenticated command injection vulnerability in multiple parameters passed to tr69_cmd.cgi. A remote attacker connected to the router's LAN and authenticated with a super user account, or using a bypass authentication vulnerability like CVE-2021-20090 could leverage this issue to run commands or gain a shell as root on the target device.
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Analysis
by VulDB Data Team • 10/14/2021
The Telus Wi-Fi Hub model PRV65B444A-S-TS represents a widely deployed consumer-grade networking device that serves as a critical entry point for residential and small business networks. This particular device operates with firmware version 3.00.20, which contains a significant authenticated command injection vulnerability that directly impacts the device's security posture and network integrity. The vulnerability resides within the tr69_cmd.cgi web interface component, which handles various configuration parameters related to the device's operation and management functions. This authentication bypass represents a particularly dangerous flaw because it allows an attacker to execute arbitrary commands with the highest possible privileges on the device's operating system.
The technical flaw manifests through improper input validation within the tr69_cmd.cgi script, which fails to adequately sanitize user-supplied parameters before processing them in system commands. When authenticated super user credentials are provided through the LAN interface, the vulnerability enables command injection attacks that can be exploited to execute arbitrary shell commands with root privileges. The vulnerability affects multiple parameters within the CGI script, making it particularly dangerous as attackers can target various input vectors to achieve their objectives. This type of vulnerability falls under CWE-77 which specifically addresses command injection flaws in software systems, where insufficient validation of user input allows attackers to inject and execute arbitrary commands.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with complete control over the device's operating environment. Once exploited, attackers can establish persistent access, modify device configurations, redirect network traffic, or use the device as a pivot point for attacks against other systems within the local network. The vulnerability's requirement for LAN access and super user authentication does not make it less dangerous, as it represents a critical weakness in the device's security model. Network administrators who rely on these devices for their network infrastructure may find their entire network compromised if they fail to properly secure the device's management interfaces and maintain updated firmware versions.
The security implications of this vulnerability align with ATT&CK technique T1059 which covers command and scripting interpreter, specifically targeting the execution of malicious commands through legitimate system interfaces. Attackers who can leverage this vulnerability can establish backdoors, install malware, or perform reconnaissance activities that would otherwise be impossible without such elevated privileges. The device's role as a network gateway makes it particularly valuable for attackers seeking to maintain persistent access to network resources while remaining undetected. Organizations should consider this vulnerability as part of a broader security assessment, particularly when evaluating the security of network infrastructure devices that lack proper input validation mechanisms.
Mitigation strategies for this vulnerability should include immediate firmware updates from Telus or the device manufacturer to address the command injection flaw. Network segmentation and access control measures should be implemented to limit LAN access to only authorized personnel, while monitoring systems should be deployed to detect unusual command execution patterns. The vulnerability highlights the importance of maintaining current firmware versions and implementing proper network access controls as recommended in NIST SP 800-125 guidelines for embedded system security. Additionally, organizations should conduct regular vulnerability assessments of their network infrastructure devices to identify similar command injection vulnerabilities that could be exploited in other systems. The presence of this vulnerability also underscores the need for robust authentication mechanisms and the principle of least privilege in network device management, as even authenticated access should not grant unlimited command execution capabilities.