Hybrid Cascade Delegation Vulnerability: A New Threat to Consumer Electronics

We identify and analyze the Hybrid Cascade Delegation (HCD) vulnerability. HCD is a complex delegation chain formed by combining NS and CNAME records. A carefully constructed HCD chain can exploit and bypass resolvers' constraints on the number of outgoing queries per resolution. This vulnerability forces a resolver to issue a large volume of queries, resulting in significant amplification of DNS traffic. Currently employed defense technologies are unable to mitigate the threats posed by this vulnerability. In modern consumer electronic devices where service endpoints are embedded and vendor-controlled, the failure of DNS resolution to the core service infrastructure can easily cause high-intensity and large-scale impact. We investigate the HCD vulnerability and address this critical issue in consumer electronic environments. We also propose and discuss mitigation solutions for the HCD vulnerability.