Description
@fastify/multipart is a multipart form-data parser for Fastify. In versions from 5.3.0 up to but not including 10.1.1, when the busboy fileSize limit truncates a file part, the plugin clears its internal current-file reference while the underlying stream is still open. If the client then aborts the connection before sending the terminating boundary, the abort cleanup finds no stream to destroy, so saveRequestFiles() never settles, the request handler hangs, and the temporary file already written to disk is never cleaned up. An unauthenticated client can repeat this to permanently leak temporary files and suspended handler executions, leading to disk and event-loop exhaustion. The issue is fixed in @fastify/multipart 10.1.1. Users should upgrade to 10.1.1.
Published: 2026-08-15
Score: 7.5 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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Tracking

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Advisories

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History

Mon, 17 Aug 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 17 Aug 2026 10:45:00 +0000

Type Values Removed Values Added
First Time appeared Fastify
Fastify fastify-multipart
Vendors & Products Fastify
Fastify fastify-multipart

Sat, 15 Aug 2026 13:45:00 +0000

Type Values Removed Values Added
Description @fastify/multipart is a multipart form-data parser for Fastify. In versions from 5.3.0 up to but not including 10.1.1, when the busboy fileSize limit truncates a file part, the plugin clears its internal current-file reference while the underlying stream is still open. If the client then aborts the connection before sending the terminating boundary, the abort cleanup finds no stream to destroy, so saveRequestFiles() never settles, the request handler hangs, and the temporary file already written to disk is never cleaned up. An unauthenticated client can repeat this to permanently leak temporary files and suspended handler executions, leading to disk and event-loop exhaustion. The issue is fixed in @fastify/multipart 10.1.1. Users should upgrade to 10.1.1.
Title @fastify/multipart vulnerable to Denial of Service via aborted upload after fileSize limit
Weaknesses CWE-400
CWE-664
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Subscriptions

Fastify Fastify-multipart
cve-icon MITRE

Status: PUBLISHED

Assigner: openjs

Published:

Updated: 2026-08-17T19:44:01.262Z

Reserved: 2026-07-31T22:18:10.089Z

Link: CVE-2026-18549

cve-icon Vulnrichment

Updated: 2026-08-17T19:43:54.762Z

cve-icon NVD

Status : Received

Published: 2026-08-15T14:17:07.590

Modified: 2026-08-17T20:16:41.567

Link: CVE-2026-18549

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-17T10:30:08Z

Weaknesses