CVE-2021-46265 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 wanBasicCfg 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-2021-46265 affects Tenda AC Series routers running firmware version AC11_V02.03.01.104_CN and represents a critical stack buffer overflow condition within the wanBasicCfg module. This type of vulnerability falls under the Common Weakness Enumeration category CWE-121, which specifically addresses stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent stack memory locations. The affected device operates as a wireless router and gateway, making it a prime target for network-level attacks that could potentially compromise the entire local network infrastructure.
The technical flaw manifests when the router processes incoming data through the wanBasicCfg module, which handles Wide Area Network basic configuration parameters. Attackers can exploit this vulnerability by crafting malicious input data that exceeds the allocated stack buffer size, causing a buffer overflow condition that leads to unpredictable program behavior and ultimately results in a denial of service state. The stack buffer overflow occurs because the implementation lacks proper input validation and bounds checking mechanisms, allowing arbitrary data to be written beyond the intended buffer boundaries. This condition can be triggered through network-based attacks that send specially crafted packets or configuration requests to the router's web interface or management ports.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides attackers with a reliable method to cause persistent denial of service conditions that can affect network connectivity for all devices relying on the compromised router. In enterprise environments, this vulnerability could lead to significant operational disruptions, particularly in scenarios where the router serves as a primary gateway for internet connectivity or network segmentation. The vulnerability's exploitation does not require authentication, making it particularly dangerous as it can be leveraged by remote attackers without prior access credentials, aligning with ATT&CK technique T1210 for exploitation of remote services. The DoS condition may also potentially be leveraged as a precursor to more sophisticated attacks, as the compromised router could be used as a staging point for further network reconnaissance or as a pivot point for attacking other network segments.
Mitigation strategies for CVE-2021-46265 should prioritize immediate firmware updates from Tenda, as the vendor has likely released patches addressing this specific buffer overflow condition. Network administrators should implement network segmentation and access control measures to limit exposure, including firewall rules that restrict access to router management interfaces from untrusted networks. The implementation of intrusion detection systems can help identify potential exploitation attempts by monitoring for unusual traffic patterns or malformed requests targeting the affected wanBasicCfg module. Additionally, regular security assessments should include vulnerability scanning for similar buffer overflow conditions across all network devices, as this represents a common class of vulnerability that affects embedded systems. Organizations should also consider implementing network monitoring solutions that can detect router restarts or service disruptions that may indicate successful exploitation of this vulnerability, as the DoS condition could be used as a covert method of network disruption without immediate detection.