CVE-2022-40069 in AC21
Summary
by MITRE • 09/19/2022
]Tenda AC21 V 16.03.08.15 is vulnerable to Buffer Overflow via /bin/httpd, function: fromSetSysTime.
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Analysis
by VulDB Data Team • 10/20/2022
The vulnerability identified as CVE-2022-40069 affects Tenda AC21 V 16.03.08.15 wireless routers, representing a critical buffer overflow condition within the device's web interface handling mechanism. This flaw exists within the /bin/httpd binary executable and specifically impacts the fromSetSysTime function, which processes system time configuration requests through the web management interface. The buffer overflow vulnerability arises when the device fails to properly validate input data length before copying it into fixed-size memory buffers, creating an exploitable condition that could allow remote code execution or system compromise.
The technical nature of this vulnerability places it squarely within the CWE-121 buffer overflow category, specifically classified as a stack-based buffer overflow when the vulnerable function processes user-supplied parameters containing system time configuration data. The flaw occurs during the parsing of HTTP requests directed to the web server component, where the device's httpd process does not implement adequate bounds checking for incoming time parameters. This allows an attacker to craft malicious HTTP requests containing oversized time data that overflows the allocated buffer space, potentially corrupting adjacent memory locations and enabling arbitrary code execution.
Operationally, this vulnerability presents significant risks to network security as it allows remote attackers to exploit the device without requiring authentication or physical access. The attack surface extends to any network user who can reach the router's web management interface, making it particularly dangerous in enterprise environments or homes where routers are exposed to external networks. Successful exploitation could result in complete device compromise, enabling attackers to gain root access to the router's operating system, modify network configurations, redirect traffic, or establish persistent backdoors for further attacks. The vulnerability also creates potential for denial-of-service conditions when the buffer overflow corrupts critical system processes.
The impact of this vulnerability extends beyond immediate device compromise to encompass broader network security implications, as compromised routers can serve as stepping stones for lateral movement within networks or as command and control centers for botnet operations. Security professionals should consider this vulnerability in relation to ATT&CK framework techniques such as T1021.001 (Remote Services: Remote Desktop Protocol) and T1071.001 (Application Layer Protocol: Web Protocols) when assessing network-wide implications. Mitigation strategies should include immediate firmware updates from Tenda, network segmentation to limit access to router management interfaces, implementation of firewall rules blocking unauthorized access to common router management ports, and monitoring for suspicious HTTP traffic patterns. Additionally, organizations should conduct comprehensive vulnerability assessments to identify other potentially affected devices and implement network access controls to prevent unauthorized access to administrative interfaces. The vulnerability highlights the critical importance of proper input validation and memory management practices in embedded systems, particularly those handling network communications and user inputs through web interfaces.