CVE-2021-45992 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 formSetQvlanList. This vulnerability allows attackers to cause a Denial of Service (DoS) via the qvlanName parameter.
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Analysis
by VulDB Data Team • 02/05/2022
The vulnerability identified as CVE-2021-45992 affects Tenda routers model G1 and G3 running firmware version v15.11.0.17(9502)_CN, representing a critical stack overflow condition within the formSetQvlanList function. This flaw resides in the router's web interface handling mechanism where user-supplied input is processed without adequate validation or bounds checking. The specific parameter qvlanName serves as the attack vector, allowing malicious actors to manipulate the device's memory structure through crafted input sequences that exceed allocated stack buffer space. The vulnerability stems from improper input sanitization practices that fail to enforce length limitations or validate user-provided data before processing.
The technical exploitation of this stack overflow vulnerability results in a denial of service condition that effectively renders the affected Tenda routers inoperable. When an attacker submits malicious input through the qvlanName parameter, the function formSetQvlanList executes without proper boundary checks, causing the stack memory to overflow and corrupt adjacent memory locations. This memory corruption typically leads to program termination or system crash, preventing legitimate users from accessing router configuration services. The vulnerability manifests as a complete service disruption requiring manual intervention or device reboot to restore normal operation. From a cybersecurity perspective, this represents a classic stack-based buffer overflow that aligns with CWE-121, which specifically addresses stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent stack memory.
The operational impact of CVE-2021-45992 extends beyond simple service interruption to potentially compromise network infrastructure availability and reliability. Network administrators responsible for managing these devices face significant operational challenges as the DoS condition can occur without warning, potentially affecting business continuity and network access for multiple users simultaneously. The vulnerability affects devices that may be deployed in critical network environments where router availability is essential for maintaining connectivity and network services. From an attacker's perspective, this vulnerability provides a straightforward path to service disruption without requiring advanced exploitation techniques or privileged access, making it particularly dangerous in environments where such devices are exposed to untrusted network traffic.
Mitigation strategies for CVE-2021-45992 should prioritize firmware updates from Tenda as the primary remediation approach, as the vendor has likely released patches addressing the stack overflow condition. Network administrators should implement network segmentation and access control measures to limit exposure of affected devices to untrusted networks, reducing the attack surface available to potential exploiters. Additional protective measures include monitoring network traffic for suspicious parameter patterns targeting the affected qvlanName parameter and implementing intrusion detection systems that can identify exploitation attempts. The vulnerability demonstrates the importance of proper input validation and buffer management in embedded systems, aligning with ATT&CK technique T1499.004 which covers network denial of service attacks. Organizations should also consider implementing device hardening practices that include disabling unnecessary services and restricting administrative access to affected devices while maintaining comprehensive network monitoring to detect anomalous behavior indicative of exploitation attempts.