CVE-2026-19474 @fastify/multipart vulnerable to Denial of Service via temporary file leak on aborted upload
An unauthenticated attacker can cause persistent disk consumption and denial of service by aborting multipart uploads, requiring an upgrade to the library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-19474?
CVE-2026-19474 is a high-severity denial of service vulnerability in @fastify/multipart, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
@fastify/multipart is a multipart form-data parser for Fastify. In versions from 3.0.0 up to but not including 10.1.1, request.saveRequestFiles() can leave completed temporary files on disk when a client disconnects while the parser is advancing between multipart parts. The iterator rejection that occurs between parts falls outside the per-file cleanup path, so an earlier completed file is never removed. An unauthenticated client can repeat this to cause persistent, linear disk consumption, leading to denial of service. This is an incomplete-fix variant of CVE-2025-24033. The issue is fixed in @fastify/multipart 10.1.1. Users should upgrade to 10.1.1.
Which versions are affected by CVE-2026-19474?
It affects 1 product.
Products include Fastify Fastify-Multipart.
How do I fix CVE-2026-19474?
No fix has been published for CVE-2026-19474 yet. Limit exposure of the affected software until one is available.
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-2026-19474 being exploited?
There is no known exploitation of CVE-2026-19474 in the wild and no public exploit code.
Other vulnerabilities in @fastify/multipart
Sources
Also known as GHSA-62qx-hpj5-j6hc.