CVE-2019-13266 in Archer C3200 V1
Summary
by MITRE
TP-Link Archer C3200 V1 and Archer C2 V1 devices have Insufficient Compartmentalization between a host network and a guest network that are established by the same device. A DHCP Request is sent to the router with a certain Transaction ID field. Following the DHCP protocol, the router responds with an ACK or NAK message. Studying the NAK case revealed that the router erroneously sends the NAK to both Host and Guest networks with the same Transaction ID as found in the DHCP Request. This allows encoding of data to be sent cross-router into the 32-bit Transaction ID field.
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Analysis
by VulDB Data Team • 12/07/2023
The vulnerability identified in TP-Link Archer C3200 V1 and Archer C2 V1 devices represents a critical flaw in network segmentation that violates fundamental security principles of isolated network environments. This issue stems from insufficient compartmentalization between host and guest networks established by the same device, creating a dangerous pathway for cross-network communication that undermines the very purpose of guest network isolation. The vulnerability specifically manifests in the DHCP protocol handling mechanism where the router fails to properly distinguish between different network segments during the NAK response process, effectively allowing malicious actors to exploit this misconfiguration to inject data across network boundaries.
The technical implementation of this vulnerability exploits the DHCP transaction ID field as a communication channel between network segments. When a DHCP request is received, the router's response mechanism incorrectly processes the NAK message by sending it to both host and guest networks simultaneously while maintaining the same transaction ID from the original request. This behavior creates a data encoding channel that allows information to be transmitted from one network segment to another through the transaction ID field, which should normally be a unique identifier for individual DHCP transactions. The 32-bit transaction ID field becomes a vector for cross-network data exfiltration and potentially malicious payload delivery, as the router's firmware does not properly validate or isolate the network context of incoming requests.
From an operational perspective, this vulnerability compromises the security posture of wireless networks by enabling unauthorized cross-network communication that violates the principle of network segmentation. Attackers can leverage this flaw to perform various malicious activities including but not limited to network reconnaissance, data exfiltration, and potentially lateral movement between network segments. The impact extends beyond simple information disclosure as it undermines the trust model of network isolation, allowing attackers to bypass security controls that are typically implemented to separate sensitive host networks from less trusted guest networks. This vulnerability is particularly concerning in enterprise environments where guest networks are commonly used to isolate visitors or IoT devices from critical corporate infrastructure.
The vulnerability aligns with CWE-668 (Exposure of Resource to Wrong Sphere) and represents a failure in proper network boundary enforcement, which is a core requirement of secure network design. It also maps to ATT&CK technique T1046 (Network Service Scanning) and T1566 (Phishing) as attackers can use this vulnerability to gather network information or deliver malicious payloads across network segments. The lack of proper input validation and network context awareness in the DHCP handling code demonstrates a fundamental flaw in the device's security architecture that allows for privilege escalation through network boundary violations. Organizations should implement immediate mitigations including firmware updates from TP-Link, network segmentation using additional security controls, and monitoring for anomalous DHCP traffic patterns that might indicate exploitation attempts. The vulnerability underscores the critical importance of proper compartmentalization in network security design and highlights the need for robust protocol implementation that maintains clear boundaries between different network contexts.