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, known as the HTTP/2 Rapid Reset Attack, is a critical vulnerability affecting nearly all HTTP/2 server implementations. Discovered on October 10, 2023, this high-severity flaw enables highly efficient Distributed Denial of Service (DDoS) attacks.

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?

The HTTP/2 Rapid Reset Attack exploits a flaw in the HTTP/2 protocol's stream cancellation mechanism. Attackers send a large number of requests and immediately cancel them, overwhelming server resources without completing full connections. This rapid reset cycle exhausts server capacity, leading to a denial of service.

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

This vulnerability enables extremely efficient DDoS attacks, allowing attackers to overwhelm servers with minimal resources. Businesses face severe service disruptions, revenue loss, and reputational damage due to inaccessible web services. Infrastructure can experience complete unavailability under sustained attacks.

http2ddosnginxhigh2023

Step-by-Step Mitigation Guide

To mitigate CVE-2023-44487, update your HTTP/2 server implementations immediately. Apply vendor-specific patches or upgrade to Nginx 1.25.3+, nghttp2 1.57.0+, or equivalent patched versions. Verify the fix by checking your server software versions and monitoring for unusual traffic patterns or resource exhaustion.

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.