TuDoor Attack: Systematically Exploring and Exploiting Logic Vulnerabilities in DNS Response Pre-processing with Malformed Packets


DNS can be compared to a game of chess in that its rules are simple, yet the possibilities it presents are endless. While the fundamental rules of DNS are straightforward, DNS implementations can be extremely complex. In this study, we intend to explore the complexities and vulnerabilities in DNS response pre-processing by systematically analyzing DNS RFCs and DNS software implementations. We present the discovery of three new types of logic vulnerabilities, leading to the proposal of three novel attacks, namely the TuDoor attack. These attacks involve the use of malformed DNS response packets to carry out DNS cache poisoning, denial-of-service, and resource consuming attacks. By performing comprehensive experiments, we demonstrate the attack’s feasibility and significant real-world impacts of TuDoor. In total, 24 mainstream DNS software, including BIND, PowerDNS, and Microsoft DNS, are affected by TuDoor. Attackers can instigate cache poisoning and denial-of-service attacks against vulnerable resolvers using a handful of crafted packets within 1 second or circumvent the query limit to deplete resolution resources (e.g., CPU). Besides, to determine the vulnerable resolver population in the wild, we collect and evaluate 16 popular Wi-Fi routers, 6 prevalent router OSes, 42 public DNS services, and around 1.8M open DNS resolvers. Our measurement results indicate that TuDoor could exploit 7 routers (OSes), 18 public DNS services, and 424,652 (23.1%) open DNS resolvers. Following the best practice of responsible disclosure, we have reported these vulnerabilities to all affected vendors, and 18 of them, including BIND, Chrome, Cloudflare, and Microsoft, have acknowledged our findings and discussed mitigation solutions with us. Furthermore, 33 CVE IDs are assigned to our discovered vulnerabilities, and we provide an online detection tool as one of the mitigation measures. Our research highlights the urgent need for standardization of DNS response pre-processing logic to enhance the security of DNS.

In Proceedings of 2024 IEEE Symposium on Security and Privacy. San Francisco, California, May 20–23, 2024. (Acceptance rate: ??%, Acceptance rate in first cycle: ??%, Acceptance rate in second cycle: ??%, Acceptance rate in third cycle: ??%).
* ✉ Corresponding authors.
* Presented in OARC 42.
* Referenced by RFC 9520: Negative Caching of DNS Resolution Failures.
* Presented in GeekCon 2024 International


This paper proposes the TuDoor Attack, by systematically exploring and exploiting logic vulnerabilities in DNS response pre-processing with malformed packets, leading to DNS cache poisoning (1s), denial-of-service, and resource consuming attacks.

TuDoor: https://tudoor.net/

CVE (33)


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 18 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 (Asia, USA, and Europe). He applied for 11 patents (1 authorized and 5 in checking as the first author). He has obtained over 200 CVE/CNVD/CNNVD vulnerability numbers, more than $11,600 rewards, 330+ GitHub stars, multiple CERT reports, 100+ news coverage, and RFC acknowledgement. He got multiple prizes, such as 1st prize of IPv6 Technology Application Innovation Competition, 2nd prize of GeekCon 2023 DAF Contest, National Scholarship, Wang Dazhong Scholarship, Tsinghua Outstanding Scholarship, and Extraordinary Hacker of GeekCon International 2024.