Unpacking the ‘HTTP/2 Rapid Reset’ Zero-Day: The New Face of DDoS Attacks

Introduction: A New Benchmark for Cyber Havoc

Imagine a world where web services can be brought to their knees, not by an army of bots but by a mere 20,000 compromised devices. This is no longer a dystopian vision; it’s the reality we face in the wake of the recently discovered zero-day vulnerability, dubbed ‘HTTP/2 Rapid Reset.¹‘ Exploited to orchestrate some of the most massive Distributed Denial of Service (DDoS) attacks ever witnessed, this new attack vector has set a disturbing precedent.

The Genesis: How HTTP/2 Rapid Reset Came to Light

In late August, cybersecurity giants like Cloudflare, Google, and Amazon Web Services (AWS) started noticing anomalous traffic patterns. These weren’t your run-of-the-mill DDoS attacks. They were “enormous, hyper-volumetric,” to borrow Cloudflare’s terminology. One attack registered at a staggering 201 million requests per second (RPS), dwarfing the previous record of 71 million RPS. Google reported a peak at an alarming 398 million RPS, and Amazon wasn’t far behind, with its largest attack peaking at 155 million RPS.

The Technical Nitty-Gritty: Understanding the Vulnerability

The underlying flaw exists in the HTTP/2 protocol, particularly in a feature known as ‘stream cancellation.’ Here’s the kicker: the attackers exploit this by initiating a request and immediately canceling it. This might seem trivial, but when automated at scale—think of a ‘request, cancel, request, cancel’ pattern—it can incapacitate servers and web applications.

This isn’t just a bug; it’s a feature turned into a weapon. The HTTP/2 protocol was designed for efficiency and speed, but its very strengths have now been twisted into vulnerabilities.

The Botnet Size Paradox: Fewer Bots, More Damage

One of the most unsettling aspects of this new DDoS methodology is the low number of compromised devices needed to execute the attack. Cloudflare reported that a mere 20,000 compromised devices were involved in the record-breaking onslaught. To put this into perspective, conventional DDoS attacks often require botnets consisting of hundreds of thousands or even millions of compromised devices.

The Current State of Mitigation: What’s Being Done?

Upon recognizing the threat, Cloudflare, Google, and AWS issued warnings and started implementing additional protective measures. These existing DDoS protections could mostly handle the HTTP/2 Rapid Reset attacks, but that’s far from a permanent solution. The vulnerability, tracked as CVE-2023-44487, has a CVSS score of 7.5, indicating high severity. Consequently, web server software companies have been alerted, and patches are in the works to prevent future exploitation.

The Wake-Up Call: Broader Implications for Cybersecurity

What the HTTP/2 Rapid Reset attacks signify is a seismic shift in the landscape of cybersecurity. The attacks have shown that no enterprise or individual is truly safe if they are serving HTTP-based workloads on the Internet. Moreover, they underscore the need for perpetual vigilance and adaptive security measures. Even the most robust of defenses can be rendered useless if not continually updated to counter new types of threats.

Conclusion: An Urgent Need for Action

The HTTP/2 Rapid Reset zero-day vulnerability² serves as a stark reminder that the cybersecurity arena is one of perpetual evolution. Attack vectors mutate, vulnerabilities are discovered, and defenses must adapt accordingly. As we grapple with the ramifications of these massive DDoS attacks, one thing is clear: complacency is not an option. Organizations must act swiftly to patch vulnerable systems and update their security postures to fend off this new breed of cyber threats.

By dissecting the HTTP/2 Rapid Reset attacks³, we not only gain a deeper understanding of this specific vulnerability but also glean invaluable insights into the ever-evolving world of cybersecurity. This is not just a call to action; it’s a call to perpetual vigilance in a digital age where threats are not just probable, but inevitable.

1. https://blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/ ↩︎
2. https://www.helpnetsecurity.com/2023/10/10/cve-2023-44487-http-2-rapid-reset/#:~:text=Decoding%20HTTP%2F2%20Rapid%20Reset%20(CVE%2D2023%2D44487)&text=This%20new%20attack%20works%20by,that%20uses%20HTTP%2F2%20offline. ↩︎
3. https://www.securityweek.com/rapid-reset-zero-day-exploited-to-launch-largest-ddos-attacks-in-history/ ↩︎