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CVE-2026-77078— multer vulnerable to Denial of Service via crafted multipart 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之前版本存在异常处理不当漏洞，该漏洞源于对multipart请求中两个特制文本字段名的处理不当，导致未捕获的RangeError（Invalid array length）并终止Node.js进程，可能允许远程攻击者造成拒绝服务。

CVSS 7.5 · High EPSS 0.49% · P41

Possible ATT&CK Techniques 1 AI

T1029 · Scheduled Transfer

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-2026-77078

Vulnerability Information
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Vulnerability Title
multer vulnerable to Denial of Service via crafted multipart 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 containing two specially crafted text field names can cause an uncaught RangeError (Invalid array length) that terminates the Node.js process. The first field uses a very large numeric array index to allocate a maximum-length sparse array, and a second field then pushes past that length, which throws inside the append-field dependency and is not caught by multer. All versions before 2.3.0 are affected, and the issue is a remotely triggerable denial of service. The issue is fixed in multer 2.3.0. Upgrade to multer 2.3.0 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
未捕获的异常
Source: CVE Program / CVE List V5
Vulnerability Title
expressjs Multer 异常处理不当漏洞
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之前版本存在异常处理不当漏洞，该漏洞源于对multipart请求中两个特制文本字段名的处理不当，导致未捕获的RangeError（Invalid array length）并终止Node.js进程，可能允许远程攻击者造成拒绝服务。
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 0 ~ 2.3.0 -

II. Public POCs for CVE-2026-77078

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III. Intelligence Information for CVE-2026-77078

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Vendor Advisories for CVE-2026-77078 (1)

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

CVE-2026-77037 7.5 HIGH multer vulnerable to Denial of Service via file descriptor leak on aborted uploads
CVE-2026-82333 7.5 HIGH multer vulnerable to Denial of Service via oversized array index in field names
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-248

V. Comments for CVE-2026-77078

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