{"id":"CVE-2026-117531","title":"@fastify/multipart vulnerable to Denial of Service via a malformed upload hanging delayed file consumers","summary":"@fastify/multipart is the multipart form-data and file upload plugin for the Fastify web framework. In versions 5.3.0 through 10.1.6, the plugin does not propagate a parser error to the file stream when a request body ends inside a file …","severity":"medium","cvss":5.9,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","cvssSource":"cna","cwe":["CWE-400"],"vendor":"@fastify/multipart","product":"@fastify/multipart","affected":["@fastify/multipart >= 5.3.0 < 10.1.7"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-02T16:58:29.940282Z"},"published":"2026-11-02","updated":"2026-11-02","sourceUpdated":"2026-11-02T16:58:46.632Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-117531","references":[{"url":"https://github.com/fastify/fastify-multipart/security/advisories/GHSA-5849-5m6q-9632"},{"url":"https://cna.openjsf.org/security-advisories.html"}],"tags":["cve.org"],"epss":0.00329,"epssPercentile":0.2616,"ingestedAt":"2026-11-05T19:30:42.715Z","slug":"CVE-2026-117531","body":"## Overview\n\n@fastify/multipart is the multipart form-data and file upload plugin for the Fastify web framework. In versions 5.3.0 through 10.1.6, the plugin does not propagate a parser error to the file stream when a request body ends inside a file part with no closing boundary, even though the Content-Length is complete, the client does not abort, and no file size limit is exceeded. The plugin destroys the in-progress file stream without an error, so a handler that iterates the request parts and performs asynchronous work before consuming the file attaches to a stream that never emits an error or end event, and the request never responds while the connection stays open. An unauthenticated remote client can repeat these malformed uploads against such a route to accumulate pending connections and exhaust server resources, so the impact is availability only and exploitation depends on the application using a delayed file consumer. The issue is fixed in @fastify/multipart 10.1.7, where the parser error is propagated to the file stream so a delayed consumer settles with an error instead of hanging, and users should upgrade to 10.1.7 or later. There is no workaround other than upgrading.\n\n## Affected\n\n- `@fastify/multipart >= 5.3.0 < 10.1.7`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":33,"depthScoreParts":{"impact":32.5,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}