{"schema":"threatline.record/2","record":{"id":"CVE-2026-19481","aliases":["GHSA-x8mw-p69m-v3mx"],"summary":"@fastify/busboy vulnerable to Denial of Service via prototype-named multipart part header","details":"### Impact\n\nVersions of `@fastify/busboy` from 1.0.0 and prior to 3.2.1 are vulnerable to a Denial of Service. The multipart header parser stores part-header names on a plain JavaScript object, so a part header named `__proto__` or `constructor` resolves to an inherited value that is not an array, and the parser throws `TypeError: this.header[h].push is not a function`. Through the documented `req.pipe(busboy)` integration this surfaces as an `error` event, while direct `write()`/`end()` usage throws synchronously and can terminate the Node.js process if uncaught. The parser runs before application middleware, so any unauthenticated client that can submit multipart/form-data is affected.\n\n### Patches\n\nFixed in version 3.2.1.\n\n### Workarounds\n\nAttach an `error` listener to the Busboy stream so the parser failure is handled rather than crashing the process, and wrap direct `write()`/`end()` calls in a try/catch. Upgrading to 3.2.1 removes the failure entirely.","categories":["Frameworks"],"product":"@fastify/busboy","vendor":"@fastify/busboy","ecosystem":"npm","affected_ranges":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-x8mw-p69m-v3mx","source_modified_at":"2026-10-02T23:17:27Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"npm","name":"@fastify/busboy"},"range":">= 1.0.0, < 3.2.1"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-19481","source_modified_at":"2026-08-13T14:25:29.262Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"@fastify/busboy","vendor":"@fastify/busboy","versions":[{"versionType":"semver","status":"affected","version":"1.0.0","lessThan":"3.2.1"},{"versionType":"semver","status":"unaffected","version":"3.2.1"}],"defaultStatus":"unaffected"},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-x8mw-p69m-v3mx","source_modified_at":"2026-10-02T23:30:05.651087437Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"npm","name":"@fastify/busboy","purl":"pkg:npm/%40fastify/busboy"},"ranges":[{"events":[{"introduced":"1.0.0"},{"fixed":"3.2.1"}],"type":"SEMVER"}],"versions":[]}],"fixed_versions":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-x8mw-p69m-v3mx","source_modified_at":"2026-10-02T23:17:27Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"npm","name":"@fastify/busboy"},"version":"3.2.1"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-19481","source_modified_at":"2026-08-13T14:25:29.262Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"@fastify/busboy","ecosystem":null},"version":"3.2.1","basis":"first unaffected version stated in the CVE record"},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-x8mw-p69m-v3mx","source_modified_at":"2026-10-02T23:30:05.651087437Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"npm","name":"@fastify/busboy","purl":"pkg:npm/%40fastify/busboy"},"version":"3.2.1"}],"cvss":7.5,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00493,"percentile":0.41478,"score_date":"2026-10-23"},"published_at":"2026-08-13T08:31:25.413Z","modified_at":"2026-10-02T23:30:05.651087437Z","provenance":[{"source":"GitHub Advisory Database","url":"https://github.com/advisories/GHSA-x8mw-p69m-v3mx","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-02T23:17:27Z"},{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-19481","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-08-13T14:25:29.262Z"},{"source":"OSV","url":"https://osv.dev/vulnerability/GHSA-x8mw-p69m-v3mx","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-02T23:30:05.651087437Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-19481","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["GitHub Advisory Database","CVE List","OSV","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/fastify/busboy/security/advisories/GHSA-x8mw-p69m-v3mx"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-19481","source":"GitHub Advisory Database"},{"url":"https://github.com/fastify/busboy/commit/957a24b66d5915e6d0a6ac988c9dbcee86373e9b","source":"GitHub Advisory Database"},{"source":"CVE List","url":"https://cna.openjsf.org/security-advisories.html"},{"url":"https://github.com/fastify/busboy/releases/tag/v3.2.1","source":"GitHub Advisory Database"},{"url":"https://github.com/advisories/GHSA-x8mw-p69m-v3mx","source":"GitHub Advisory Database"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","ssvc":{"exploitation":"none","automatable":"yes","technical_impact":"partial","assessed_at":"2026-08-13T14:25:06.775682Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-02T23:30:05.651087437Z","content_hash":"ff84398ecd77261dcae8cd1456b0ea3e61347994c124e4b5f87abe20d83c940a"}}