Uncaught Exception in Fastify - CVE-2026-120216
Published: November 6, 2026
Vulnerability identifier: #VU159840
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-120216
CWE-ID: CWE-248
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows an unauthenticated remote attacker to crash a Fastify server and interrupt other in-flight requests.
The vulnerability exists due to an uncaught exception in Fastify when a nonzero handlerTimeout expires after a streaming response has sent its headers. An unauthenticated remote attacker can send a single request to an affected streaming endpoint whose response remains open past the timeout, causing the Node.js process to terminate.
Affected software
Fastify
How to mitigate CVE-2026-120216
Install security update from vendor's website.
Fastify - update to 5.12.8