CVE-2022-40071 in AC21
Summary
by MITRE • 09/19/2022
Tenda AC21 V 16.03.08.15 is vulnerable to Buffer Overflow via /bin/httpd, formSetDeviceName.
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Analysis
by VulDB Data Team • 10/20/2022
The vulnerability identified as CVE-2022-40071 affects the Tenda AC21 wireless router firmware version 16.03.08.15 and represents a critical buffer overflow condition within the web interface handling component. This flaw exists in the /bin/httpd binary module specifically when processing the formSetDeviceName parameter, creating a potential pathway for remote code execution and system compromise. The affected device operates with a web server component that fails to properly validate input length before copying data into fixed-size buffers, a classic programming error that has been documented in numerous security advisories and vulnerability assessments.
The technical implementation of this vulnerability stems from improper input validation within the device's HTTP daemon which processes web form submissions. When a remote attacker sends a specially crafted request containing an excessively long string to the formSetDeviceName parameter, the application fails to enforce bounds checking before copying the data into a predetermined buffer space. This buffer overflow condition allows an attacker to overwrite adjacent memory locations, potentially corrupting the program execution flow and enabling arbitrary code execution with the privileges of the web server process. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a direct violation of secure coding practices that emphasize input validation and memory safety.
The operational impact of this vulnerability extends beyond simple denial of service or data corruption scenarios. An unauthenticated remote attacker could leverage this buffer overflow to execute malicious code on the affected router, potentially gaining full administrative control over the device. This compromise could enable attackers to modify network configurations, redirect traffic through malicious proxies, establish persistent backdoors, or use the device as a launching point for further attacks within the local network. The vulnerability particularly affects the device's ability to maintain network security boundaries, as it allows attackers to subvert the router's role as a security gateway and potentially access connected devices and resources. The attack surface is significant given that many home and small office routers remain accessible from the internet without proper network segmentation or firewall rules.
Mitigation strategies for this vulnerability should prioritize immediate firmware updates from the vendor, as the manufacturer has likely released patches addressing the buffer overflow condition. Network administrators should implement strict firewall rules to limit access to the router's web interface from untrusted networks, while also ensuring that the device's administrative interface is not exposed to the public internet. Additional defensive measures include monitoring network traffic for suspicious requests containing unusually long parameter values, implementing network segmentation to isolate critical systems, and conducting regular security assessments of network infrastructure. The vulnerability demonstrates the importance of applying security patches promptly and adheres to ATT&CK technique T1210, which involves exploitation of remote services through buffer overflow conditions. Organizations should also consider implementing intrusion detection systems that can identify potential exploitation attempts targeting known vulnerabilities in network infrastructure devices.