CVE-2021-46262 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 PPPoE 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-2021-46262 affects Tenda AC Series routers running firmware version AC11_V02.03.01.104_CN and potentially other models in the AC series. This issue resides within the PPPoE module of the router's firmware, representing a critical security flaw that could be exploited by remote attackers to disrupt network services. The vulnerability manifests as a stack buffer overflow condition that occurs when the router processes specific malformed data within the PPPoE protocol handling mechanism.
The technical implementation of this buffer overflow stems from inadequate input validation within the PPPoE module where the router fails to properly bounds-check data received during PPPoE session establishment or maintenance. When attackers send specifically crafted packets containing oversized or malformed data to the PPPoE service, the router's stack memory becomes corrupted, leading to unpredictable behavior and ultimately causing the device to crash or become unresponsive. This vulnerability falls under CWE-121 Stack-based Buffer Overflow, which is classified as a fundamental memory safety issue that has been consistently identified as a high-risk vulnerability in network infrastructure devices.
From an operational perspective, this vulnerability creates significant risk for network availability and business continuity. The DoS condition can be triggered remotely without authentication requirements, making it particularly dangerous as attackers can disrupt network services simply by sending malicious packets to the router's PPPoE service. The impact extends beyond individual device compromise as it affects the entire network infrastructure that relies on these devices for internet connectivity, potentially causing widespread service disruption for organizations and households dependent on the affected routers. This vulnerability directly maps to ATT&CK technique T1499.004 Network Denial of Service, which involves the exploitation of network services to cause service unavailability.
Mitigation strategies for this vulnerability should prioritize immediate firmware updates from Tenda's official sources, as the manufacturer has likely released patches addressing this specific buffer overflow condition. Network administrators should also implement network segmentation and access control measures to limit exposure of these devices to untrusted networks, while monitoring for unusual traffic patterns that might indicate exploitation attempts. Additionally, implementing intrusion detection systems that can identify malformed PPPoE packets may provide early warning of attempted exploitation. Organizations should conduct comprehensive vulnerability assessments of their network infrastructure to identify other potentially affected devices and ensure that all firmware versions are kept current with security patches. The vulnerability demonstrates the critical importance of proper input validation and memory management in embedded network devices, particularly those handling network protocol processing functions that are essential for connectivity and service availability.