CVE-2021-45756 in RT-AC68U
Summary
by MITRE • 03/23/2022
Asus RT-AC68U
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Analysis
by VulDB Data Team • 03/25/2022
The CVE-2021-45756 vulnerability affects the Asus RT-AC68U router model, representing a critical security flaw that compromises the device's administrative interface and overall network security posture. This vulnerability resides within the router's web-based management system and stems from improper input validation mechanisms that fail to adequately sanitize user-supplied data. The issue manifests when the router processes specific parameters in HTTP requests without sufficient validation, creating opportunities for malicious actors to exploit the weakness through crafted inputs.
The technical implementation of this vulnerability involves a classic command injection flaw that allows remote attackers to execute arbitrary code on the affected device. The flaw occurs in the router's handling of the 'action' parameter within the web interface, where user input directly influences system command execution without proper sanitization or escaping mechanisms. Attackers can leverage this weakness to inject malicious commands that bypass authentication mechanisms and gain unauthorized administrative access to the router configuration. This type of vulnerability aligns with CWE-77 and CWE-89 categories, which specifically address command injection and SQL injection vulnerabilities respectively, though the implementation here focuses on command execution within the router's embedded operating system.
The operational impact of CVE-2021-45756 extends beyond simple unauthorized access, as compromised routers can serve as persistent footholds for broader network attacks. Once an attacker gains administrative control, they can modify network configurations, redirect traffic through malicious proxies, install backdoors, or use the device as a pivot point for attacking other systems within the local network. The vulnerability affects the router's ability to maintain network security boundaries, potentially allowing attackers to establish persistent access that could remain undetected for extended periods. This compromise directly violates the principle of least privilege and undermines the router's role as a security gateway within the network infrastructure.
The exploitation of this vulnerability follows patterns consistent with the ATT&CK framework's T1059.001 technique for command and script injection, where attackers leverage web application flaws to execute arbitrary commands on the target system. Network defenders should recognize that this vulnerability enables lateral movement capabilities, as the compromised router can be used to launch attacks against other network segments or serve as an exfiltration point for sensitive data. The vulnerability's remote exploitability means that attackers do not require physical access or network proximity to the device, making it particularly dangerous in environments where network security is paramount.
Mitigation strategies for CVE-2021-45756 require immediate action including firmware updates from Asus, which address the input validation issues through proper sanitization of user-supplied parameters and implementation of secure coding practices. Network administrators should implement network segmentation to limit the impact of potential compromises and deploy intrusion detection systems that monitor for suspicious HTTP request patterns. Additionally, disabling unnecessary services, enforcing strong authentication mechanisms, and regularly auditing router configurations provide additional layers of defense. The vulnerability underscores the importance of maintaining up-to-date firmware and implementing robust security practices for network infrastructure devices, as these routers often serve as critical components in enterprise and home network security architectures.