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CVE-2026-120216

fastify is a web framework for Node.js

Risk score
45/100
CVSS
5.9 v3.1
Published
2 Nov 2026

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What to know

What it is
fastify is a web framework for Node.js. In versions 5.8.0 through 5.12.7, when the server is configured with a nonzero handlerTimeout and a route returns a streaming response, a request whose stream has already sent its headers but stays open past the timeout crashes the server. When the timeout fires, Fastify tries t…
Affected
See advisory
Fix
Upgrade the product to 5.12.8 or later.
Exploitation
No known exploitation

Why it is Yellow

  • CVSS 5.9 medium
  • On your watchlist: node.js

References

Original description

fastify is a web framework for Node.js. In versions 5.8.0 through 5.12.7, when the server is configured with a nonzero handlerTimeout and a route returns a streaming response, a request whose stream has already sent its headers but stays open past the timeout crashes the server. When the timeout fires, Fastify tries to send a new error response on a response that has already started, raising an uncaught ERR_HTTP_HEADERS_SENT that terminates the Node.js process and interrupts any other in-flight requests. An unauthenticated remote client can trigger this with a single request to an affected streaming endpoint, so the impact is availability only, and exploitation requires the non-default handlerTimeout to be set. The default handlerTimeout of 0 is not affected. The issue is fixed in fastify 5.12.8, and users should upgrade to 5.12.8 or later. As a workaround, set handlerTimeout to 0, which disables the affected timeout path.

Last activity 2 Nov 2026. Patch Forecast updates every hour.