@fastify/multipart vulnerable to Denial of Service via a malformed upload hanging delayed file consumers

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-117531
StatePUBLISHED
Assigneropenjs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-02 11:17:30 UTC
Updated2026-11-02 17:17:38 UTC
Description@fastify/multipart is the multipart form-data and file upload plugin for the Fastify web framework. In versions 5.3.0 through 10.1.6, the plugin does not propagate a parser error to the file stream when a request body ends inside a file part with no closing boundary, even though the Content-Length is complete, the client does not abort, and no file size limit is exceeded. The plugin destroys the in-progress file stream without an error, so a handler that iterates the request parts and performs asynchronous work before consuming the file attaches to a stream that never emits an error or end event, and the request never responds while the connection stays open. An unauthenticated remote client can repeat these malformed uploads against such a route to accumulate pending connections and exhaust server resources, so the impact is availability only and exploitation depends on the application using a delayed file consumer. The issue is fixed in @fastify/multipart 10.1.7, where the parser error is propagated to the file stream so a delayed consumer settles with an error instead of hanging, and users should upgrade to 10.1.7 or later. There is no workaround other than upgrading.

Risk And Classification

Primary CVSS: v3.1 5.9 MEDIUM from ce714d77-add3-4f53-aff5-83d477b104bb

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-400 | CWE-400 CWE-400: Uncontrolled Resource Consumption

VersionSourceTypeScoreSeverityVector
3.1ce714d77-add3-4f53-aff5-83d477b104bbSecondary5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNACVSS5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA @fastifymultipart @fastify/multipart affected 5.3.0 10.1.7 semver Not specified
CNA @fastifymultipart @fastify/multipart unaffected 10.1.7 semver Not specified

References

ReferenceSourceLinkTags
cna.openjsf.org/security-advisories.html ce714d77-add3-4f53-aff5-83d477b104bb cna.openjsf.org
github.com/fastify/fastify-multipart/security/advisories/GHSA-5849-5m6q-... ce714d77-add3-4f53-aff5-83d477b104bb github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: fifoqueue (en)

CNA: mcollina (en)

CNA: UlisesGascon (en)

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