The Maginot Line: Attacking the Boundary of DNS Caching Protection


Xiang Li, Chaoyi Lu, and Baojun Liu, Tsinghua University; Qifan Zhang and Zhou Li, University of California, Irvine; Haixin Duan, Tsinghua University, QI-ANXIN Technology Research Institute, and Zhongguancun Laboratory; Qi Li, Tsinghua University and Zhongguancun Laboratory


In this paper, we report MaginotDNS, a powerful cache poisoning attack against DNS servers that simultaneously act as forwarder and recursive resolver (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 assigned, 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.

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@inproceedings {285515,
author = {Xiang Li and Chaoyi Lu and Baojun Liu and Qifan Zhang and Zhou Li and Haixin Duan and Qi Li},
title = {The Maginot Line: Attacking the Boundary of {DNS} Caching Protection},
booktitle = {32nd USENIX Security Symposium (USENIX Security 23)},
year = {2023},
isbn = {978-1-939133-37-3},
address = {Anaheim, CA},
pages = {3153--3170},
url = {},
publisher = {USENIX Association},
month = aug

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