CVE-2026-18549Network attack vector

Service exhaustion via aborted truncated uploads

Published Aug 15, 2026 · Updated Aug 15, 2026

Resource exhaustion in Fastify @fastify/multipart 5.3.0 through 10.1.0 allows remote attackers to hang handlers via aborted uploads. When a file exceeds the busboy fileSize limit, the plugin clears its current-file reference before the stream closes, leaving abort cleanup unable to destroy the stream or remove its temporary file. Exposure requires an application to call request.saveRequestFiles() with a fileSize limit; repeated unauthenticated requests consume disk space and suspend handler executions until service capacity is exhausted.

CVSS severity7.5
High
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Fastify @fastify/multipart 5.3.0 through 10.1.0 allows remote attackers to hang handlers via aborted uploads. When a file exceeds the busboy fileSize limit, the plugin clears its current-file reference before the stream closes, leaving abort cleanup unable to destroy the stream or remove its temporary file. Exposure requires an application to call request.saveRequestFiles() with a fileSize limit; repeated unauthenticated requests consume disk space and suspend handler executions until service capacity is exhausted.

The record

CVE
CVE-2026-18549
Published
Aug 15, 2026
Updated
Aug 15, 2026
Vendor
Fastify
Product
@fastify/multipart
Classifications
CWE-400, CWE-664, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.3.0 <10.1.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Fastify · @fastify/multipartversion=5.3.0 <10.1.1

Published CVSS scores

7.5OpenJS FoundationCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
CWE-664Improper Control of a Resource Through its Lifetime
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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