CVE-2021-46321 in AC11
Summary
by MITRE • 02/15/2022
Tenda AC Series Router AC11_V02.03.01.104_CN was discovered to contain a stack buffer overflow in the wifiBasicCfg module. This vulnerability allows attackers to cause a Denial of Service (DoS) via crafted overflow data.
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Analysis
by VulDB Data Team • 02/18/2022
The vulnerability identified as CVE-2021-46321 affects the Tenda AC Series Router model AC11_V02.03.01.104_CN and represents a critical stack buffer overflow flaw within the wifiBasicCfg module. This type of vulnerability falls under the common weakness enumeration CWE-121 which specifically addresses stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations on the program stack. The affected device operates with a web-based management interface that processes configuration parameters through the wifiBasicCfg module, creating an attack surface that can be exploited by remote malicious actors.
The technical implementation of this vulnerability stems from improper input validation within the router's firmware code where user-supplied data is directly copied into a fixed-size stack buffer without adequate boundary checks. When an attacker crafts malicious input data and sends it to the vulnerable router through the wifiBasicCfg interface, the buffer overflow occurs during the processing of wireless configuration parameters. This flaw enables attackers to manipulate the program execution flow by overwriting return addresses, stack canaries, or other critical memory locations, ultimately leading to system instability and potential arbitrary code execution capabilities. The attack vector requires network access to the router's web management interface and can be executed remotely without authentication.
The operational impact of CVE-2021-46321 manifests primarily as a denial of service condition that can render the affected router completely inoperable. When exploited successfully, the stack buffer overflow causes the router to crash and restart repeatedly, creating a persistent denial of service for all network services including wireless connectivity, internet access, and administrative functions. Network administrators may experience complete loss of network connectivity for devices connected to the affected router, potentially disrupting business operations and personal network services. The vulnerability affects all devices running the specific firmware version mentioned, making it particularly concerning for widespread deployment scenarios where multiple routers may be simultaneously vulnerable.
Mitigation strategies for this vulnerability should prioritize immediate firmware updates from Tenda to address the buffer overflow condition in the wifiBasicCfg module. Network administrators should implement network segmentation and access controls to limit exposure of affected routers to untrusted networks while monitoring for suspicious traffic patterns that may indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1210 which covers exploitation of remote services, and organizations should consider implementing intrusion detection systems to monitor for patterns consistent with buffer overflow exploitation attempts. Additionally, network administrators should conduct comprehensive inventory assessments to identify all affected devices and implement temporary network isolation measures until firmware patches are deployed. The remediation process must include thorough testing of firmware updates in controlled environments before deployment to production networks to ensure that the patch does not introduce compatibility issues with existing network configurations.