CVE-2026-82333Network attack vector

Request-processing hang via sparse-array field parsing

Published Aug 28, 2026 · Updated Aug 28, 2026

Denial of service in Express.js Multer before 2.3.0 allows remote attackers to block Node.js request handling via crafted multipart fields. The append-field parser allocates a maximum-length sparse array for a large numeric field index, then synchronously traverses it when a second field adds a non-numeric key. One unauthenticated HTTP request to a route that invokes Multer is enough to monopolize the event loop and interrupt all request processing in that Node.js process.

CVSS severity7.5
High
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Express.js Multer before 2.3.0 allows remote attackers to block Node.js request handling via crafted multipart fields. The append-field parser allocates a maximum-length sparse array for a large numeric field index, then synchronously traverses it when a second field adds a non-numeric key. One unauthenticated HTTP request to a route that invokes Multer is enough to monopolize the event loop and interrupt all request processing in that Node.js process.

The record

CVE
CVE-2026-82333
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
body-parser
Product
Multer
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 28, 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=0 <2.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

body-parser · Multerversion=0 <2.3.0

Published CVSS scores

7.5GitHubCVSS: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.

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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
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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