| Package | Affected versions | Patched versions |
|---|---|---|
| fastify | < 5.7.3 | 5.7.3 |
| fastify | < 5.7.3 | 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.
The issue is fixed in Fastify 5.7.3. Users should upgrade to 5.7.3 or later.
Avoid sending Web Streams from Fastify responses (e.g., ReadableStream or Response bodies). Use Node.js streams (stream.Readable) or buffered payloads instead until the project can upgrade.
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