What is CVE-2023-44487?

The HTTP/2 Rapid Reset Attack exploits the stream cancellation feature to overwhelm servers with a fraction of normal traffic, enabling massive DDoS attacks. Affected virtually all HTTP/2 implementations.

How do I fix CVE-2023-44487?

Update nginx to 1.25.3+, Apache to 2.4.58+, and apply all vendor patches. Enable Cloudflare or CDN-level DDoS protection. Set http2_max_concurrent_streams to a low value (e.g., 128) in nginx. Implement rate limiting on HTTP/2 connections at the edge. Monitor for traffic spikes and RESET_STREAM frames. Consider disabling HTTP/2 on exposed endpoints if not required.

highCVSS 7.5/10·Published: 2023-10-10·HTTP/2 servers (nginx, Apache, Node.js, Go, AWS, Cloudflare)

How to fix CVE-2023-44487 – Step-by-Step Guide

CVE-2023-44487, the HTTP/2 Rapid Reset DDoS Attack, is a high-severity vulnerability impacting virtually all HTTP/2 server implementations. Published October 10, 2023, it enables highly efficient denial-of-service attacks with minimal attacker resources.

CVE ID

CVE-2023-44487

Severity

HIGH

CVSS Score

7.5/10

Affected

HTTP/2 servers (nginx, Apache, Node.js, Go, AWS, Cloudflare)

What is HTTP/2 Rapid Reset DDoS Attack?

This vulnerability exploits the HTTP/2 protocol's stream cancellation feature. Attackers rapidly open and close streams on a single connection, overwhelming server resources without completing requests. This rapid reset behavior consumes CPU and memory, leading to denial of service for affected HTTP/2 servers.

Affected Versions

All HTTP/2 server implementations (pre-patch)

Fixed In

Nginx 1.25.3+, nghttp2 1.57.0+, vendor-specific patches

Official References

Impact and Risks for your Infrastructure

The HTTP/2 Rapid Reset attack enables extremely efficient DDoS attacks using minimal attacker resources and few connections. This can lead to severe service disruptions, website unavailability, and significant operational costs. Infrastructure can be overwhelmed by a fraction of normal traffic, causing widespread outages.

http2ddosnginxhigh2023

Step-by-Step Mitigation Guide

Mitigate CVE-2023-44487 by immediately updating all HTTP/2 server implementations to patched versions. For Nginx, upgrade to 1.25.3+ or 1.24.0+. Consult vendor-specific advisories for other software like Apache, Node.js, or Go. Verify the fix by checking server versions and monitoring for unusual HTTP/2 stream activity.

1Update nginx to 1.25.3+, Apache to 2.4.58+, and apply all vendor patches.
2Enable Cloudflare or CDN-level DDoS protection.
3Set http2_max_concurrent_streams to a low value (e.g., 128) in nginx.
4Implement rate limiting on HTTP/2 connections at the edge.
5Monitor for traffic spikes and RESET_STREAM frames.
6Consider disabling HTTP/2 on exposed endpoints if not required.

Frequently Asked Questions

What is the CVSS score for CVE-2023-44487?▼

CVE-2023-44487 has a CVSS score of 7.5/10 (high severity). This reflects a significant security risk that should be addressed promptly.

Which versions of HTTP/2 servers (nginx, Apache, Node.js, Go, AWS, Cloudflare) are affected?▼

Affected: All HTTP/2 server implementations (pre-patch). The vulnerability was fixed in: Nginx 1.25.3+, nghttp2 1.57.0+, vendor-specific patches.

How long does it take to fix CVE-2023-44487?▼

For most teams: 15–60 minutes to apply the patch, plus 15 minutes of post-patch verification. Complex multi-service environments may require 2–4 hours including staging validation.

Is CVE-2023-44487 being actively exploited?▼

Check the NVD entry and CISA KEV catalog for exploitation status. As a high-severity vulnerability, treat it as a priority remediation regardless of known exploitation status.

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This CVE fix guide is based on publicly available security advisories (NVD, vendor bulletins). Always test changes in a staging environment before applying to production. Verify against the official vendor advisory for the most up-to-date guidance.