CVE-2026-25224
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
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| fastify | fastify | to 5.7.3 (exc) |
Helpful Resources
Exploitability
| 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. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
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.
How can this vulnerability impact me? :
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.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
Can you explain this vulnerability to me?
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.
How can this vulnerability impact me? :
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.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
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.
What immediate steps should I take to mitigate this vulnerability?
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.