{"id":"CVE-2026-19484","aliases":["GHSA-xjh9-v7x6-24jw"],"title":"@fastify/busboy vulnerable to Denial of Service via oversized multipart boundary","summary":"@fastify/busboy vulnerable to Denial of Service via oversized multipart boundary","severity":"high","cvss":7.5,"cwe":["CWE-835","CWE-1322"],"vendor":"fastify","product":"@fastify/busboy","ecosystem":"npm","affected":["@fastify/busboy >= 3.1.0, < 3.2.1"],"patched":["@fastify/busboy 3.2.1"],"published":"2026-10-02","updated":"2026-10-02","sourceUpdated":"2026-10-02T23:17:29Z","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-xjh9-v7x6-24jw","references":[{"url":"https://github.com/fastify/busboy/security/advisories/GHSA-xjh9-v7x6-24jw"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-19484"},{"url":"https://github.com/fastify/busboy/commit/632a237e7fb6b3b7a30e0de8fab2ee72ca5bf722"},{"url":"https://cna.openjsf.org/security-advisories.html"},{"url":"https://github.com/fastify/busboy/releases/tag/v3.2.1"},{"url":"https://github.com/advisories/GHSA-xjh9-v7x6-24jw"}],"tags":["ghsa","npm"],"epss":0.00615,"epssPercentile":0.47573,"ingestedAt":"2026-10-02T23:34:57.390Z","slug":"CVE-2026-19484","body":"## Overview\n\n### Impact\n\nVersions of `@fastify/busboy` from 3.1.0 and prior to 3.2.1 are vulnerable to a Denial of Service. The vendored streaming multipart search stores its default skip distance in a `Uint8Array(256)`. A multipart boundary of exactly 252 bytes makes the search needle 256 bytes, and the table entry wraps to zero, so a crafted request keeps the search in a CPU-bound loop and stalls the Node.js event loop. An unauthenticated client can trigger this with a single small request. Applications that use `@fastify/busboy` to parse multipart/form-data, directly or through `@fastify/multipart`, are affected.\n\n### Patches\n\nFixed in version 3.2.1.\n\n### Workarounds\n\nValidate the multipart boundary before parsing and reject any boundary longer than the RFC 2046 limit of 70 characters (for example at a reverse proxy or in an onRequest hook). Upgrading to 3.2.1 removes the issue.\n\n## Affected packages\n\n- `@fastify/busboy >= 3.1.0, < 3.2.1`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `@fastify/busboy 3.2.1`","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}