CVE-2021-45995 in Tenda
Summary
by MITRE • 02/04/2022
Tenda routers G1 and G3 v15.11.0.17(9502)_CN were discovered to contain a stack overflow in the function formSetStaticRoute. This vulnerability allows attackers to cause a Denial of Service (DoS) via the staticRouteNet, staticRouteMask, and staticRouteGateway parameters.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 02/05/2022
The vulnerability identified as CVE-2021-45995 affects Tenda routers model G1 and G3 running firmware version v15.11.0.17(9502)_CN, representing a critical stack overflow condition within the formSetStaticRoute function. This flaw resides in the router's web interface handling mechanism where user-supplied parameters are processed without adequate input validation or bounds checking. The specific parameters staticRouteNet, staticRouteMask, and staticRouteGateway serve as entry points for malicious input that can trigger the exploitable condition. The vulnerability manifests through the manipulation of these network routing parameters, which are typically used for configuring static routes within the router's routing table. When an attacker submits malformed data through these parameters, the router's processing function fails to properly validate the input length, leading to a buffer overflow that corrupts the stack memory structure. This stack corruption fundamentally disrupts the router's normal operation and can result in immediate system instability.
The technical execution of this vulnerability follows a classic stack buffer overflow pattern that aligns with CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The affected function formSetStaticRoute likely employs a fixed-size buffer to store user-provided network parameters without proper length verification, creating an exploitable condition where input data exceeds the allocated buffer space. The attack vector is particularly concerning as it operates through the router's web administration interface, making it accessible to remote attackers without requiring physical access or specialized equipment. The vulnerability can be exploited via HTTP requests containing maliciously crafted parameters that cause the router to crash and restart, effectively creating a denial of service condition that disrupts network connectivity for all connected devices.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire network infrastructure. When the DoS condition occurs, the router becomes unresponsive and requires manual intervention to restore functionality, typically involving a power cycle or firmware reinstallation. Network administrators may experience extended downtime while investigating and resolving the issue, particularly in environments where router availability is critical for business operations. The vulnerability affects the router's ability to maintain stable routing tables and network connectivity, potentially causing cascading failures in larger network deployments where multiple routers depend on proper static route configuration. Organizations relying on Tenda G1 and G3 routers for their network infrastructure face significant risk of service interruption, especially in scenarios where automated network management systems depend on consistent router availability.
Mitigation strategies for CVE-2021-45995 should focus on immediate firmware updates from Tenda to address the stack overflow vulnerability, as this represents the most effective solution to prevent exploitation. Network administrators should implement network segmentation and access controls to limit exposure of affected routers to untrusted networks, utilizing firewall rules to restrict access to the router's web administration interface. The implementation of intrusion detection systems can help identify potential exploitation attempts through monitoring of malformed HTTP requests targeting the vulnerable parameters. Additionally, regular vulnerability assessments and network scanning should be conducted to identify other potentially affected devices within the network infrastructure. Organizations should also consider implementing automated backup and recovery procedures to minimize downtime during restoration processes, while maintaining detailed logs of router configuration changes to facilitate rapid incident response. The vulnerability highlights the importance of proper input validation and bounds checking in embedded network devices, aligning with ATT&CK technique T1210 for exploitation of software vulnerabilities and emphasizing the need for robust secure coding practices in network infrastructure equipment.