Vulnerability in @fastify/busboy (CVE-2026-74866)
Summary
Vulnerability in @fastify/busboy (CVE-2026-74866). Risk of unauthorized operations or information disclosure. Exploitable via filename. Mitigation: upgrade to 3.2.2 or later.
Original description
The description as published by the source.
Impact
@fastify/busboy 3.2.1 and earlier retains a bare carriage return or line feed inside the parsed Content-Disposition parameters returned to the application. The multipart header parser ends a header line only on the two-byte \r\n sequence, so a lone CR or LF embedded in a part header is carried verbatim into the filename and field name delivered by the file and field events. An application that forwards the supplied filename or name into a CR/LF-sensitive sink cannot anticipate the embedded control character.
An attacker who uploads a file whose filename or field name contains a bare CR or LF can pollute filenames on disk when the upload is saved under its original name, inject forged lines into logs, or inject headers on a downstream hop that does not re-validate CR/LF, such as object-storage metadata or a proxied backend. Applications using @fastify/busboy directly, or through @fastify/multipart and its consumers, are affected.
Patches
Upgrade to @fastify/busboy 3.2.2 or later.
Workarounds
Validate or strip carriage return and line feed characters from the filename and field name before using them in any filesystem, logging, or outbound-header context.
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-2026-74866 has been found in @fastify/busboy.
Attackers can target a specific entry point like filename over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.8/10.
What to do: upgrade @fastify/busboy to 3.2.2 or later.
If unsure, ask your IT team or search "@fastify/busboy CVE-2026-74866" on the vendor's site.
CVE-2026-74866 (@fastify/busboy) — CWE-93 / CVSS v3 5.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: filename / name / file / field
Patched: 3.2.2 — apply immediately
Workaround: Validate or strip carriage return and line feed characters from the filename and field name before using them in any filesystem, logging, or outbound-header context.
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-93) exists in @fastify/busboy. Attackers reach the vulnerable code path via filename without authentication.
Check the vendor advisory for the affected versions of @fastify/busboy. Attack surface: filename / name / file / field.
Severity: Medium (CVSS 5.8/10). Risk of unauthorized operations or information disclosure.
Update to 3.2.2.
Workaround: Validate or strip carriage return and line feed characters from the filename and field name before using them in any filesystem, logging, or outbound-header context.
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 or strip carriage return and line feed characters from the `filename` and field `name` before using them in any filesystem, logging, or outbound-header context.パッチが適用されるまでの応急処置として、Validate or strip carriage return and line feed characters from the
filenameand fieldnamebefore using them in any filesystem, logging, or outbound-header context. を実施。回避策の副作用 (機能低下) を確認した上で。 -
3Apply patch patch
Upgrade @fastify/busboy to 3.2.2ステージング環境で 3.2.2 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。
-
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 nvd.nist.gov
- package github.com
- web cna.openjsf.org
- web github.com
- web github.com
- web github.com
- web github.com