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CVE-2026-5079— multer vulnerable to Denial of Service via deeply nested field names

Quick assessment

Affected
multer multer
Exploitation
Public or AI PoC available; prioritize validation
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 1.0.0版本至2.2.0之前版本和3.0.0-alpha.1版本至3.0.0-alpha.2之前版本存在资源管理错误漏洞，该漏洞源于嵌套字段名解析无限制，可能导致攻击者通过特制的多部分表单数据强制分配深度嵌套的对象结构，消耗CPU和内存，造成拒绝服务。

CVSS 7.5 · High EPSS 0.49% · P40

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 4

VendorProduct Version RangeStatus
multer multer 1.0.0< 2.2.0 affected
2.2.0 unaffected
3.0.0-alpha.1< 3.0.0-alpha.2 affected
3.0.0-alpha.2 unaffected
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I. Basic Information for CVE-2026-5079

Vulnerability Information
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Vulnerability Title
multer vulnerable to Denial of Service via deeply nested field names
Source: CVE Program / CVE List V5
Vulnerability Description
Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names with no limit on nesting depth, allowing an attacker to force allocation of deeply nested object structures that consume CPU and memory. A single HTTP request with a crafted multipart body is sufficient to exploit this. Patches: Users should upgrade to multer 2.2.0 (2.x line) or 3.0.0-alpha.2 (3.x prerelease) and configure the new limits.fieldNestingDepth option to the minimum depth their application requires. Workarounds: Set limits.fields to a reasonable value to reduce the number of fields an attacker can send per request. This does not fully mitigate the issue but limits the impact.
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 1.0.0版本至2.2.0之前版本和3.0.0-alpha.1版本至3.0.0-alpha.2之前版本存在资源管理错误漏洞，该漏洞源于嵌套字段名解析无限制，可能导致攻击者通过特制的多部分表单数据强制分配深度嵌套的对象结构，消耗CPU和内存，造成拒绝服务。
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 1.0.0 ~ 2.2.0 -

II. Public POCs for CVE-2026-5079

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 6589 chars
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III. Intelligence Information for CVE-2026-5079

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Vendor Advisories for CVE-2026-5079 (1)

IV. Related Vulnerabilities

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

V. Comments for CVE-2026-5079

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