{"affected":[{"defaultStatus":"unaffected","ecosystem":"npm","packageName":"fastify","product":"fastify","source":"CNA: openjs","vendor":"fastify","versions":[{"lessThan":"5.12.8","status":"affected","version":"5.8.0","versionType":"semver"},{"status":"unaffected","version":"5.12.8","versionType":"semver"}]}],"cveId":"CVE-2026-120216","cwes":["CWE-248"],"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.","epss":null,"exploits":[],"kev":null,"metrics":[{"score":5.9,"severity":"medium","source":"CNA: openjs","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},{"score":5.9,"severity":"medium","source":"NVD: ce714d77-add3-4f53-aff5-83d477b104bb","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"}],"modifiedAt":1793618251553,"publishedAt":1793617680038,"references":[{"source":"CNA: openjs","tags":[],"url":"https://github.com/fastify/fastify/security/advisories/GHSA-3qgw-9275-xf8w"},{"source":"CNA: openjs","tags":[],"url":"https://cna.openjsf.org/security-advisories.html"},{"source":"ce714d77-add3-4f53-aff5-83d477b104bb","tags":[],"url":"https://cna.openjsf.org/security-advisories.html"},{"source":"ce714d77-add3-4f53-aff5-83d477b104bb","tags":[],"url":"https://github.com/fastify/fastify/security/advisories/GHSA-3qgw-9275-xf8w"}],"remediation":[],"revision":"fbaf1f566026682c9925367dfc7c1644611507f3cb119be325b62d318a107147","sources":[{"modifiedAt":1793617680038,"name":"CNA: openjs","retrievedAt":1793621315696,"url":"https://www.cve.org/CVERecord?id=CVE-2026-120216"},{"modifiedAt":1793618251553,"name":"NVD","retrievedAt":1793621824180,"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-120216"}],"ssvc":null,"status":"published","title":"fastify vulnerable to Denial of Service via uncaught exception on handlerTimeout with streaming responses","updatedAt":1793621824180}