CVE-2026-25224 Fastify Vulnerable to DoS via Unbounded Memory Allocation in sendWebStream
Remote attackers can exhaust server memory and cause crashes by exploiting unbounded buffering in Fastify's Web Streams response handling.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-25224?
CVE-2026-25224 is a low-severity denial of service vulnerability in fastify, published on 3 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-770
Which versions are affected by CVE-2026-25224?
2 open source packages ship an affected version, including fastify. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
fastify npm | All versions | 5.7.3 |
fastify npm | All versions | 5.7.3 |
Products include Fastify Fastify.
How do I fix CVE-2026-25224?
Upgrade fastify to 5.7.3 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-25224 being exploited?
There is no known exploitation of CVE-2026-25224 in the wild and no public exploit code.
Other vulnerabilities in fastify
- CVE-2026-84504 fastify vulnerable to request body replacement via an async validation result collision
- CVE-2026-76169 fastify vulnerable to authentication bypass via malformed URLs reaching encapsulated not-found handlers
- CVE-2026-84428 fastify vulnerable to header validation bypass via incomplete schema case normalization
- CVE-2026-84469 fastify vulnerable to request validation bypass via skipped boolean false schemas
- CVE-2026-33806 fastify vulnerable to Body Schema Validation Bypass via Leading Space in Content-Type Header
Sources
Also known as GHSA-mrq3-vjjr-p77c, MINI-9cqm-r9jm-fgm6.