CVE-2026-25224
Unknown Unknown - Not Provided
Denial-of-Service in Fastify Web Streams Causes Memory Exhaustion

Publication date: 2026-02-03

Last updated on: 2026-02-10

Assigner: GitHub, Inc.

Description
Fastify is a fast and low overhead web framework, for Node.js. Prior to version 5.7.3, a denial-of-service vulnerability in Fastify’s Web Streams response handling can allow a remote client to exhaust server memory. Applications that return a ReadableStream (or Response with a Web Stream body) via reply.send() are impacted. A slow or non-reading client can trigger unbounded buffering when backpressure is ignored, leading to process crashes or severe degradation. This issue has been patched in version 5.7.3.
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Meta Information
Published
2026-02-03
Last Modified
2026-02-10
Generated
2026-06-16
AI Q&A
2026-02-04
EPSS Evaluated
2026-06-14
NVD
CVE-2026-25224
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
fastify fastify to 5.7.3 (exc)
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-770 The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.
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Executive Summary

This vulnerability exists in Fastify, a Node.js web framework, prior to version 5.7.3. It involves the handling of Web Streams responses where applications return a ReadableStream or a Response with a Web Stream body using reply.send(). A remote client can exploit this by sending data slowly or not reading the response, which causes unbounded buffering due to ignored backpressure. This can exhaust the server's memory.

Impact Analysis

The vulnerability can lead to denial-of-service conditions by exhausting server memory. This can cause the Fastify process to crash or experience severe performance degradation, potentially making the application unavailable to legitimate users.

Compliance Impact

I don't know

Detection Guidance

I don't know

Executive Summary

This vulnerability exists in Fastify, a Node.js web framework, prior to version 5.7.3. It is a denial-of-service issue related to how Fastify handles Web Streams responses. Specifically, when an application returns a ReadableStream or a Response with a Web Stream body using reply.send(), a remote client that reads data slowly or not at all can cause the server to buffer data without limit. This unbounded buffering happens because backpressure is ignored, which can exhaust the server's memory and lead to crashes or severe performance degradation.

Impact Analysis

The impact of this vulnerability is primarily a denial-of-service condition. A remote attacker can cause the Fastify server to consume excessive memory resources by sending requests that trigger unbounded buffering of Web Streams responses. This can result in the server process crashing or experiencing severe performance degradation, potentially making the application unavailable to legitimate users.

Compliance Impact

I don't know

Detection Guidance

I don't know

Mitigation Strategies

To mitigate this vulnerability, you should upgrade Fastify to version 5.7.3 or later, where the issue has been patched.

Avoid returning a ReadableStream or Response with a Web Stream body via reply.send() in affected versions, as this can trigger unbounded buffering and lead to denial-of-service.

Mitigation Strategies

To mitigate this vulnerability, you should upgrade Fastify to version 5.7.3 or later, where the issue has been patched.

Additionally, avoid returning a ReadableStream or Response with a Web Stream body via reply.send() in affected versions, as this can trigger unbounded buffering leading to denial-of-service.

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