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 high-severity vulnerability (CVSS 7.5) affecting virtually all HTTP/2 server implementations. This widespread flaw enables highly efficient Distributed Denial of Service (DDoS) attacks. Immediate patching is crucial to protect your infrastructure.

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 protocol's stream cancellation mechanism. Attackers repeatedly send requests and immediately cancel them, creating a massive backlog of pending streams on the server. This rapid stream reset consumes server resources disproportionately, leading to service disruption with minimal attacker traffic.

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 and a fraction of normal traffic. Businesses face severe service outages, reputational damage, and potential financial losses due to system unavailability. Infrastructure becomes highly susceptible to disruption.

http2ddosnginxhigh2023

Step-by-Step Mitigation Guide

To mitigate CVE-2023-44487, update your HTTP/2 server implementations immediately. Apply vendor-specific patches, such as Nginx 1.25.3+ or nghttp2 1.57.0+. Verify the fix by checking your server's version and monitoring for unusual traffic patterns or resource spikes post-patching.

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.