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CVE-2026-82333— multer vulnerable to Denial of Service via oversized array index in field names

Quick assessment

Affected
multer multer
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

expressjs Multer是expressjs组织开源的一个用于Node.js中间件。 expressjs Multer 2.3.0之前版本存在资源管理错误漏洞，该漏洞源于对特制文本字段名处理不当，导致字段解析器同步迭代最大长度稀疏数组并阻塞事件循环，可能造成远程拒绝服务攻击。

CVSS 7.5 · High EPSS 0.49% · P41

Possible ATT&CK Techniques 1 AI

T1027 · Obfuscated Files or Information

Affected Version Matrix 2

VendorProduct Version RangeStatus
multer multer < 2.3.0 affected
2.3.0 unaffected
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I. Basic Information for CVE-2026-82333

Vulnerability Information
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Vulnerability Title
multer vulnerable to Denial of Service via oversized array index in field names
Source: CVE Program / CVE List V5
Vulnerability Description
multer is a middleware for handling multipart/form-data in Node.js. A small multipart request with two specially crafted text field names can make multer's field parser synchronously iterate a maximum-length sparse array, blocking the event loop so the process cannot handle other requests. A large numeric array index in the first field allocates a maximum-length sparse array, and a second field with a non-numeric key then triggers a full-length iteration inside the append-field dependency. All versions before 2.3.0 are affected, and this is a remotely triggerable denial of service. multer 2.3.0 adds an opt-in fieldArrayIndexLimit option that rejects oversized array indexes. Upgrade to multer 2.3.0 and set limits.fieldArrayIndexLimit to the largest array index your application needs to remediate.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
expressjs Multer 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
expressjs Multer是expressjs组织开源的一个用于Node.js中间件。 expressjs Multer 2.3.0之前版本存在资源管理错误漏洞，该漏洞源于对特制文本字段名处理不当，导致字段解析器同步迭代最大长度稀疏数组并阻塞事件循环，可能造成远程拒绝服务攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
multer multer 0 ~ 2.3.0 -

II. Public POCs for CVE-2026-82333

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III. Intelligence Information for CVE-2026-82333

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Vendor Advisories for CVE-2026-82333 (1)

Same Patch Batch · multer · 2026-08-28 · 4 CVEs total

CVE-2026-77078 7.5 HIGH multer vulnerable to Denial of Service via crafted multipart field names
CVE-2026-77037 7.5 HIGH multer vulnerable to Denial of Service via file descriptor leak on aborted uploads
CVE-2026-77063 3.7 LOW multer vulnerable to file size limit bypass via async fileFilter race condition

IV. Related Vulnerabilities

Same product: multer
Same vendor: multer
Same weakness: CWE-400

V. Comments for CVE-2026-82333

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