Security | Threat Detection | Cyberattacks | DevSecOps | Compliance

Welcome to the 23rd edition of Cloudflare’s Quarterly DDoS Threat Report. This report offers a comprehensive analysis of the evolving threat landscape of Distributed Denial of Service (DDoS) attacks based on data from the Cloudflare network. In this edition, we focus on the third quarter of 2025.

Cloudflare has deployed a new protection to address a vulnerability in React Server Components (RSC). All Cloudflare customers are automatically protected, including those on free and paid plans, as long as their React application traffic is proxied through the Cloudflare Web Application Firewall (WAF). Cloudflare Workers are inherently immune to this exploit. React-based applications and frameworks deployed on Workers are not affected by this vulnerability.

As the surface area for attacks on the web increases, Cloudflare’s Web Application Firewall (WAF) provides a myriad of solutions to mitigate these attacks. This is great for our customers, but the cardinality in the workloads of the millions of requests we service means that generating false positives is inevitable. This means that the default configuration we have for our customers has to be fine-tuned.

We have some big news to share today: Replicate, the leading platform for running AI models, is joining Cloudflare. We first started talking to Replicate because we shared a lot in common beyond just a passion for bright color palettes. Our mission for Cloudflare’s Workers developer platform has been to make building and deploying full-stack applications as easy as possible. Meanwhile, Replicate has been on a similar mission to make deploying AI models as easy as writing a single line of code.

As bots and agents start cryptographically signing their requests, there is a growing need for website operators to learn public keys as they are setting up their service. I might be able to find the public key material for well-known fetchers and crawlers, but what about the next 1,000 or next 1,000,000? And how do I find their public key material in order to verify that they are who they say they are? This problem is called discovery.

The way we interact with the Internet is changing. Not long ago, ordering a pizza meant visiting a website, clicking through menus, and entering your payment details. Soon, you might just ask your phone to order a pizza that matches your preferences. A program on your device or on a remote server, which we call an AI agent, would visit the website and orchestrate the necessary steps on your behalf.

The Internet is in the midst of one of the most complex transitions in its history: the migration to post-quantum (PQ) cryptography. Making a system safe against quantum attackers isn't just a matter of replacing elliptic curves and RSA with PQ alternatives, such as ML-KEM and ML-DSA. These algorithms have higher costs than their classical counterparts, making them unsuitable as drop-in replacements in many situations.

On April 10th, 2025 12:10 UTC, a security researcher notified Cloudflare of two vulnerabilities (CVE-2025-4820 and CVE-2025-4821) related to QUIC packet acknowledgement (ACK) handling, through our Public Bug Bounty program. These were DDoS vulnerabilities in the quiche library, and Cloudflare services that use it. quiche is Cloudflare's open-source implementation of QUIC protocol, which is the transport protocol behind HTTP/3.

The world is in a race to build its first quantum computer capable of solving practical problems not feasible on even the largest conventional supercomputers. While the quantum computing paradigm promises many benefits, it also threatens the security of the Internet by breaking much of the cryptography we have come to rely on. To mitigate this threat, Cloudflare is helping to migrate the Internet to Post-Quantum (PQ) cryptography.

The era of agentic commerce is coming, and it brings with it significant new challenges for security. That’s why Cloudflare is partnering with Visa and Mastercard to help secure automated commerce as AI agents search, compare, and purchase on behalf of consumers. Through our collaboration, Visa developed the Trusted Agent Protocol and Mastercard developed Agent Pay to help merchants distinguish legitimate, approved agents from malicious bots.