The Maginot Line: Attacking the Boundary of DNS Caching Protection


In this paper, we report MaginotDNS, a powerful cache poisoning attack against DNS servers that simultaneously act as recursive resolvers and forwarders (termed as CDNS). The attack is made possible through exploiting vulnerabilities in the bailiwick checking algorithms, one of the cornerstones of DNS security since the 1990s, and affects multiple versions of popular DNS software, including BIND and Microsoft DNS. Through field tests, we find that the attack is potent, allowing attackers to take over entire DNS zones, even including Top-Level Domains (e.g., .com and .net). Through a large-scale measurement study, we also confirm the extensive usage of CDNSes in real-world networks (up to 41.8% of our probed open DNS servers) and find that at least 35.5% of all CDNSes are vulnerable to MaginotDNS. After interviews with ISPs, we show a wide range of CDNS use cases and real-world attacks. We have reported all the discovered vulnerabilities to DNS software vendors and received acknowledgments from all of them. 3 CVE-ids have been published, and 2 vendors have fixed their software. Our study brings attention to the implementation inconsistency of security checking logic in different DNS software and server modes (i.e., recursive resolvers and forwarders), and we call for standardization and agreements among software vendors.

In Proceedings of the 32nd USENIX Security Symposium. Anaheim, California, August 9–11, 2023. (Acceptance rate: 422/1,444=29.2%, Acceptance rate in summer: 91/388=23.5%, Acceptance rate in fall: 155/531=29.2%, Acceptance rate in winter: 176/525=33.5%).
* Presented in Black Hat USA 2023.
* 60+ news coverage by media such as BleepingComputer.
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In this paper, we report MaginotDNS, a powerful cache poisoning attack against DNS servers that simultaneously act as recursive resolvers and forwarders (termed as CDNS).


CVE (3)


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Xiang Li
Xiang Li
Ph.D. Candidate in Cyberspace Security (Tsinghua University)

Xiang Li is a 5th-year Ph.D. candidate at the Institute of Network Science and Cyberspace, Tsinghua University, advised by Professors Qi Li and Haixin Duan. His research interests include network security, protocol security, IPv6 security, DNS security, Internet measurement, network & protocol fuzzing, network vulnerability discovery & attack, and underground economy with 12 research papers. As the first author, he has published many research papers at all top-tier security conferences, including Oakland S&P, USENIX Security, CCS, NDSS, and Black Hat. He has obtained over 180 CVE/CNVD vulnerability numbers, more than $11,600 rewards, multiple CERT reports, 60+ news coverage, and RFC acknowledgement. He got multiple prizes, such as 1st prize of IPv6 Technology Application Innovation Competition, Tsinghua Outstanding Scholarship, and LongFor Excellent Scholarship.