CVE-2022-40067 in AC21
Summary
by MITRE • 09/19/2022
Tenda AC21 V 16.03.08.15 is vulnerable to Buffer Overflow via /bin/httpd, function: formSetVirtualSer.
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Analysis
by VulDB Data Team • 10/20/2022
The vulnerability identified as CVE-2022-40067 affects the Tenda AC21 V 16.03.08.15 wireless router firmware, specifically targeting the web server component that handles HTTP requests. This device operates with a web interface for configuration management and the vulnerability manifests within the /bin/httpd binary which serves as the embedded web server. The flaw occurs within the formSetVirtualSer function, indicating that the buffer overflow vulnerability is triggered when processing form data submitted through the web interface.
This buffer overflow vulnerability represents a critical security weakness that stems from improper input validation within the web server implementation. The issue arises from insufficient bounds checking when handling user-supplied data in the form processing logic. When an attacker submits a malformed request containing excessive data to the formSetVirtualSer function, the system fails to properly validate the input length before copying it into a fixed-size buffer. This allows the attacker to overwrite adjacent memory locations, potentially leading to arbitrary code execution or system crash.
The operational impact of this vulnerability extends beyond simple denial of service, as it provides a potential pathway for remote code execution on the affected device. Attackers could leverage this flaw to gain unauthorized access to the router's administrative interface, modify network configurations, redirect traffic, or establish persistent backdoors. The vulnerability affects the device's web management interface which typically requires authentication, but the buffer overflow could potentially be exploited to bypass authentication mechanisms or escalate privileges. The embedded nature of the web server in the router firmware means that successful exploitation could compromise the entire network infrastructure.
The technical implementation of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory. This flaw also relates to ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation could enable attackers to execute arbitrary commands on the device. The vulnerability exists in the HTTP server component that handles user input through web forms, making it accessible via standard web browser interaction. The affected function formSetVirtualSer suggests this is related to virtual server configuration management, indicating that the buffer overflow could potentially manipulate network routing or service configurations.
Mitigation strategies for this vulnerability should prioritize immediate firmware updates from Tenda, as the manufacturer likely released patches addressing the buffer overflow condition. Network administrators should implement additional security controls including firewall rules that restrict access to the router's web management interface, particularly from untrusted networks. The implementation of network segmentation and access control lists can help limit the potential impact if exploitation occurs. Regular firmware updates and security audits of network infrastructure should be maintained to prevent similar vulnerabilities. Additionally, monitoring for unusual network traffic patterns or unauthorized configuration changes could help detect exploitation attempts. The vulnerability underscores the importance of input validation and proper memory management in embedded systems, particularly those with network-facing services that handle user input.