Vulnerability in @fastify/busboy (CVE-2026-19484)
Summary
Vulnerability in @fastify/busboy (CVE-2026-19484). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 3.2.1 or later.
Original description
The description as published by the source.
@fastify/busboy is a multipart form-data parser. In versions 3.1.0 through 3.2.0, a remote unauthenticated attacker can stall the Node.js event loop by sending a multipart request whose boundary is crafted to a specific length. The vendored streaming search stores its skip table in a fixed 256 entry byte array, and a boundary of exactly 252 bytes makes the search needle 256 bytes, which truncates the default skip distance to zero and turns the search into a CPU bound loop on a small body. A single small request can keep one core busy and deny service to other requests handled by the same process. The issue is fixed in @fastify/busboy 3.2.1, which widens the skip table so the skip distance is preserved. Users should upgrade to 3.2.1.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-19484 has been found in @fastify/busboy.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade @fastify/busboy to 3.2.1 or later.
If unsure, ask your IT team or search "@fastify/busboy CVE-2026-19484" on the vendor's site.
CVE-2026-19484 (@fastify/busboy) — CWE-835 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 3.2.1 — apply immediately
Workaround: Validate 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).
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-835) exists in @fastify/busboy.
Check the vendor advisory for the affected versions of @fastify/busboy.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 3.2.1.
Workaround: Validate 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).
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r '@fastify/busboy' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r '@fastify/busboy' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
@fastify/busboyを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
Validate 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).パッチが適用されるまでの応急処置として、Validate 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). を実施。回避策の副作用 (機能低下) を確認した上で。
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3Apply patch patch
Upgrade @fastify/busboy to 3.2.1ステージング環境で 3.2.1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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4Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory cna.openjsf.org
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- web github.com
- web github.com
- web github.com