CVE-2026-120216 (GCVE-0-2026-120216)
Vulnerability from cvelistv5 – Published: 2026-11-02 11:08 – Updated: 2026-11-02 16:56
VLAI
EPSS
VEX
Title
fastify vulnerable to Denial of Service via uncaught exception on handlerTimeout with streaming responses
Summary
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.
Severity
5.9 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-11-02 16:55 UTC
CWE
- CWE-248 - Uncaught Exception
Assigner
References
Impacted products
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