# HTTP/2 Rapid Reset: record-breaking DDoS attacks (CVE-2023-44487) · pwn.watch

> Attackers abused HTTP/2 stream cancellation (open a request, reset it right away, repeat) to make servers do work at enormous rates. Peaks hit 398M req/s at Google, 201M at Cloudflare and 155M at AWS. Almost every HTTP/2 server and proxy needed a fix, including Node.js, Go, Java servers, .NET/IIS and nginx.

Page: https://pwn.watch/i/http2-rapid-reset-ddos-cve-2023-44487 · generated 2026-10-23T04:59:28.006Z

## Status
- Severity: high · status: closed · patch: patched
- Product: HTTP/2 protocol implementations (servers, proxies, CDNs)
- Started: 2023-08-25 · closed: 2023-10-10
- CVEs: CVE-2023-44487
- Affected: Most HTTP/2 implementations; see each vendor's advisory
- Fixed in: See vendor advisories (each HTTP/2 implementation shipped its own fix)

## Follow this incident
- RSS (one item per update): https://pwn.watch/i/http2-rapid-reset-ddos-cve-2023-44487/feed.xml
- JSON Feed: https://pwn.watch/i/http2-rapid-reset-ddos-cve-2023-44487/feed.json
- Full data (timeline, sources, posts, agentBrief): https://pwn.watch/i/http2-rapid-reset-ddos-cve-2023-44487.json
- This file: https://pwn.watch/i/http2-rapid-reset-ddos-cve-2023-44487/llms.txt

## Updates (newest first)
- 2023-10-10: Coordinated disclosure by Google, Cloudflare and AWS; CISA adds CVE-2023-44487 to KEV (https://cloud.google.com/blog/products/identity-security/how-it-works-the-novel-http2-rapid-reset-ddos-attack)
- 2023-08-25: Cloudflare starts seeing unusually large HTTP/2 attacks (https://blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/)

## Fix brief
# Security brief: HTTP/2 Rapid Reset: record-breaking DDoS attacks (CVE-2023-44487)

Source: https://pwn.watch/i/http2-rapid-reset-ddos-cve-2023-44487 · status: closed (closed Oct 10, 2023) · severity: high · updated Oct 10, 2023

## Patch status
**PATCHED: fixed releases exist. Upgrade to a fixed version.**

## What it is
Attackers abused HTTP/2 stream cancellation (open a request, reset it right away, repeat) to make servers do work at enormous rates. Peaks hit 398M req/s at Google, 201M at Cloudflare and 155M at AWS. Almost every HTTP/2 server and proxy needed a fix, including Node.js, Go, Java servers, .NET/IIS and nginx.

Severity detail: CVSS 7.5 (NVD), exploited in the wild Aug–Oct 2023 (CISA KEV)

- Product: HTTP/2 protocol implementations (servers, proxies, CDNs)
- CVE / advisory ids: CVE-2023-44487

## Affected versions
- Most HTTP/2 implementations; see each vendor's advisory

## Check whether you're affected
No generic command applies (the product is a hosted service, appliance or desktop app). Check the installed version in its admin UI / About screen and compare with the versions above.

## Fix
Upgrade to one of these fixed versions (or later on the same branch):
- See vendor advisories (each HTTP/2 implementation shipped its own fix)

After upgrading, re-run the checks above and redeploy/restart the affected services.

## Latest updates
- Oct 10, 2023: Coordinated disclosure by Google, Cloudflare and AWS; CISA adds CVE-2023-44487 to KEV
- Aug 25, 2023: Cloudflare starts seeing unusually large HTTP/2 attacks

## Advisories
- [NVD: CVE-2023-44487](https://nvd.nist.gov/vuln/detail/CVE-2023-44487) (NVD)
- [CISA Known Exploited Vulnerabilities Catalog](https://www.cisa.gov/known-exploited-vulnerabilities-catalog) (CISA)

## Write-ups & news
- [HTTP/2 Rapid Reset: deconstructing the record-breaking attack](https://blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/)
- [How it works: The novel HTTP/2 'Rapid Reset' DDoS attack](https://cloud.google.com/blog/products/identity-security/how-it-works-the-novel-http2-rapid-reset-ddos-attack)

## Caveats
Stacks: Node.js, Go (x/net/http2), Java servers (Tomcat, Jetty, Netty) and .NET/IIS all shipped fixes; check your runtime's own advisory.

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Machine-readable: https://pwn.watch/i/http2-rapid-reset-ddos-cve-2023-44487.json · all incidents: https://pwn.watch/incidents.json. Verify against the vendor advisory before changing production systems.