CVE-2021-41383 in R6020
Summary
by MITRE • 09/18/2021
setup.cgi on NETGEAR R6020 1.0.0.48 devices allows an admin to execute arbitrary shell commands via shell metacharacters in the ntp_server field.
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Analysis
by VulDB Data Team • 09/22/2021
The vulnerability identified as CVE-2021-41383 affects NETGEAR R6020 routers running firmware version 1.0.0.48 and potentially other affected models. This issue resides within the setup.cgi web interface component that handles network time protocol server configuration. The vulnerability represents a critical command injection flaw that enables authenticated administrative users to execute arbitrary system commands through malicious input manipulation. The specific vector involves the ntp_server parameter field where shell metacharacters can be injected to bypass input validation mechanisms.
This vulnerability falls under CWE-77 which categorizes improper neutralization of special elements used in a command, specifically manifesting as command injection. The flaw occurs when the device fails to properly sanitize user input before incorporating it into system commands, creating an environment where attackers can manipulate the execution flow of the underlying operating system. The ntp_server field serves as the attack surface where malicious characters such as semicolons, ampersands, or backticks can be inserted to chain commands. The authentication requirement for exploitation means that an attacker must first obtain administrative credentials, though this does not significantly reduce the risk given the severity of potential system compromise.
The operational impact of this vulnerability extends beyond simple command execution to potentially enable full system compromise and persistent access. An attacker with administrative privileges could leverage this flaw to install backdoors, modify firewall rules, disable security features, or exfiltrate sensitive data from the network. The attack surface is particularly concerning for enterprise environments where these devices may serve as primary network gateways, potentially providing lateral movement opportunities to internal systems. Network monitoring tools may not immediately detect malicious command execution as it appears to be legitimate administrative activity, making detection more challenging.
Mitigation strategies should focus on immediate firmware updates from NETGEAR to address the command injection vulnerability, as well as implementing network segmentation to limit the blast radius of potential exploitation. Organizations should enforce strong administrative credential policies including multi-factor authentication and regular credential rotation. Network access controls should restrict administrative access to these devices to trusted networks only, while implementing monitoring for unusual command execution patterns in system logs. The ATT&CK framework categorizes this vulnerability under T1059.001 for command and scripting interpreter, with potential progression to T1078 for valid accounts and T1566 for social engineering if attackers leverage compromised administrative credentials. Regular security assessments should include verification of device firmware versions and input validation mechanisms to prevent similar vulnerabilities from persisting in network infrastructure components.