CVE-2021-33964 in An Lianbao WF-1
Summary
by MITRE • 01/18/2022
China Mobile An Lianbao WF-1 V1.0.1 router provides a web interface /api/ZRRuleFilter/set_firewall_level which receives parameters by POST request, and the parameter firewall_level has a command injection vulnerability. An attacker can use the vulnerability to execute remote commands.
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Analysis
by VulDB Data Team • 01/20/2022
The CVE-2021-33964 vulnerability affects the China Mobile An Lianbao WF-1 V1.0.1 router, representing a critical command injection flaw in the device's web interface. This vulnerability exists within the /api/ZRRuleFilter/set_firewall_level endpoint which processes POST requests containing a firewall_level parameter. The flaw stems from inadequate input validation and sanitization mechanisms, allowing malicious actors to inject arbitrary commands that are subsequently executed by the router's underlying operating system. The vulnerability specifically targets the firewall level configuration functionality, which typically controls network traffic filtering rules and security policies. This command injection vulnerability enables attackers to execute arbitrary code on the affected device with the privileges of the web application process, potentially compromising the entire network infrastructure.
The technical exploitation of this vulnerability follows standard command injection patterns where user-supplied input is directly incorporated into system commands without proper sanitization. The firewall_level parameter serves as the attack vector, where an attacker can craft malicious payloads that bypass input filters and execute operating system commands. This type of vulnerability maps directly to CWE-77 and CWE-94, which classify command injection and code injection respectively. The attack surface is particularly concerning as it allows remote code execution without requiring authentication, making it a significant threat to network security. The vulnerability demonstrates poor input validation practices and highlights the importance of implementing proper sanitization mechanisms for all user-controllable parameters in web applications.
The operational impact of this vulnerability extends beyond simple remote code execution, creating substantial risks for network infrastructure security. An attacker could potentially gain complete control over the router's functionality, including access to network traffic filtering rules, firewall configurations, and potentially sensitive network data. The compromised device could serve as a foothold for further network infiltration, enabling lateral movement attacks against other connected devices. Additionally, the router could be used as a pivot point for launching attacks against internal network systems or as a command and control server for botnet activities. This vulnerability affects enterprise and residential networks alike, with potentially severe consequences for organizations relying on the device for network security. The impact is further amplified by the fact that the vulnerability is remotely exploitable, requiring no physical access or local network presence to compromise the device.
Mitigation strategies for CVE-2021-33964 should prioritize immediate firmware updates from China Mobile if available, as this represents the most effective solution to address the underlying code flaws. Network administrators should implement strict network segmentation and monitor for unusual network traffic patterns that might indicate exploitation attempts. The principle of least privilege should be enforced by restricting access to the router's web interface to authorized personnel only, while also implementing strong authentication mechanisms. Security monitoring should include detection of suspicious POST requests to the vulnerable endpoint, particularly those containing shell metacharacters or command injection patterns. Organizations should also consider implementing network intrusion detection systems that can identify and block malicious payloads targeting this specific vulnerability. According to ATT&CK framework, this vulnerability aligns with T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation. Regular vulnerability assessments and network scanning should be conducted to identify similar flaws in other network devices, as this represents a common pattern in embedded device security implementations. The vulnerability underscores the critical need for secure coding practices and input validation in network infrastructure devices, particularly those handling sensitive configuration parameters.