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Medium, CVSS 5.8amended

@fastify/busboy vulnerable to CRLF injection via multipart Content-Disposition filename and name

CVE-2026-74866GHSA-gxm5-99cw-xjw9

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (@fastify/busboy 3.2.2), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
5.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
EPSS
  • CVE-2026-74866: 0.33% estimated exploitation activity in the next 30 days; percentile 25.75 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-gxm5-99cw-xjw9

  2. Revision 2 · amended ·

    Amended from osv record GHSA-gxm5-99cw-xjw9

  3. Revision 1 · created ·

    Published from ghsa record GHSA-gxm5-99cw-xjw9

Agent brief

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# Patch Next advisory brief: CVE-2026-74866

Advisory: @fastify/busboy vulnerable to CRLF injection via multipart Content-Disposition filename and name
IDs: CVE-2026-74866, GHSA-gxm5-99cw-xjw9
Record: https://patchnext.com/advisories/cve-2026-74866 (revision 3, source checked 26 Oct 2026, 13:06 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @fastify/busboy 3.2.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @fastify/busboy: affected < 3.2.2; fixed in 3.2.2

## Suggested inspection (read-only)
- `npm ls @fastify/busboy --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @fastify/busboy.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-gxm5-99cw-xjw9 (GitHub-reviewed advisory GHSA-gxm5-99cw-xjw9 lists affected ranges: npm @fastify/busboy >=0 <3.2.2)
- Verified: https://osv.dev/vulnerability/GHSA-gxm5-99cw-xjw9 (OSV record GHSA-gxm5-99cw-xjw9 lists affected ranges: npm @fastify/busboy >=0 <3.2.2 (fixed))

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