CVE-2022-40076 in AC21
Summary
by MITRE • 09/19/2022
Tenda AC21 V16.03.08.15 is vulnerable to Buffer Overflow via /bin/httpd, function: fromSetWifiGusetBasic.
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Analysis
by VulDB Data Team • 10/20/2022
The vulnerability identified as CVE-2022-40076 affects Tenda AC21 routers running firmware version V16.03.08.15 and represents a critical buffer overflow condition within the web server component of the device. This flaw exists in the /bin/httpd binary and specifically impacts the fromSetWifiGusetBasic function, which handles guest Wi-Fi configuration settings through the web interface. The buffer overflow occurs when processing user-supplied input parameters that are passed to this function, creating an exploitable condition that could allow remote code execution or system compromise.
The technical implementation of this vulnerability stems from improper input validation and memory management within the web server daemon. When a remote attacker sends specially crafted HTTP requests containing malicious data to the affected router's web interface, the system fails to properly bounds-check the input before copying it into a fixed-size buffer. This classic buffer overflow condition allows attackers to overwrite adjacent memory locations, potentially corrupting program execution flow and enabling arbitrary code execution with the privileges of the web server process. The vulnerability falls under CWE-121, which specifically addresses stack-based buffer overflow conditions, and represents a significant risk due to the privileged nature of the httpd process running on the router.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass complete system compromise and potential network infiltration. Attackers could leverage this vulnerability to gain unauthorized access to the router's administrative interface, modify network configurations, intercept or manipulate network traffic, and establish persistent access points within the network. The affected Tenda AC21 device operates with elevated privileges, meaning successful exploitation could provide attackers with complete control over the device's functionality, including access to guest Wi-Fi networks, network settings, and potentially other connected devices. This vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter, as the attacker could execute arbitrary commands on the compromised device.
Mitigation strategies for CVE-2022-40076 should prioritize immediate firmware updates from Tenda, as the vendor has likely released patches addressing this specific buffer overflow condition. Network administrators should implement additional security controls including network segmentation to isolate affected devices, disable unnecessary services and ports, and deploy intrusion detection systems to monitor for suspicious traffic patterns. The principle of least privilege should be applied by ensuring that only authorized personnel have access to the router's administrative interface, and multi-factor authentication should be implemented where possible. Regular network monitoring and vulnerability scanning should be conducted to identify other potentially affected devices within the network infrastructure, as similar vulnerabilities may exist in other router models or firmware versions. Organizations should also consider implementing network access control measures and firewall rules to restrict access to the router's web interface from untrusted networks.