CVE-2026-5079: Multer Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-72gw-mp4g-v24j
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CVSS 7.5
CWE-400
Published
Advisory Summary

CVE-2026-5079 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Multer libraries in the npm ecosystem. The issue involves multer vulnerable to denial of service via deeply nested field names. Remediation is available by upgrading affected packages to version 2.2.0, 3.0.0-alpha.2.

CVE-2026-5079 at a Glance

CVE Identifier CVE-2026-5079
GHSA Identifier GHSA-72gw-mp4g-v24j
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Multer
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-5079

To remediate this vulnerability, upgrade all affected Multer dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

multer fixed: 2.2.0 
npm install multer@2.2.0
multer fixed: 3.0.0-alpha.2 
npm install multer@3.0.0-alpha.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls multer

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-5079, inspect your project dependencies using npm:

npm ls multer

Analyze the terminal output to locate any version of Multer in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.2.0), your application is affected.

Note: The npm ls multer command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Multer, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Multer is vulnerable to a Denial of Service (DoS) via deeply nested field names in multipart form data. The `append-field` dependency parses bracket notation in field names (e.g., `a[b][c]`) 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 `2.2.0` and configure `limits.fieldNestingDepth` 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.

CVE-2026-5079 Affected Multer Versions

2 component(s)
Fixed Versions:
2.2.03.0.0-alpha.2
Product / Package Ecosystem Affected Versions Fixed Version
multer
npm/multer
npm
≥ 1.0.0
< 2.2.0
2.2.0
multer
npm/multer
npm
≥ 3.0.0-alpha.1
< 3.0.0-alpha.2
3.0.0-alpha.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24j
NVD — CVE-2026-5079 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-5079
Multer Security Information SECURITY
https://cna.openjsf.org/security-advisories.html
Multer Source Repository REPOSITORY
https://github.com/expressjs/multer

Frequently Asked Questions

What is CVE-2026-5079?
CVE-2026-5079 is a security vulnerability in Multer involving Multer vulnerable to Denial of Service via deeply nested field names under CWE-400: Uncontrolled Resource Consumption.
Which Multer versions are affected?
Affected versions include releases prior to 2.2.0, 3.0.0-alpha.2 across affected packages: multer.
What version fixes CVE-2026-5079?
Upgrading to 2.2.0, 3.0.0-alpha.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is multer affected?
Yes, multer is affected in releases prior to 2.2.0, 3.0.0-alpha.2. Upgrade your dependency to 2.2.0, 3.0.0-alpha.2 or later.
What is the CVSS score of CVE-2026-5079?
CVE-2026-5079 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-5079?
CVE-2026-5079 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check npm dependencies for CVE-2026-5079?
Run the dependency tree command: 'npm ls multer'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-72gw-mp4g-v24j",
  "modified" : "2026-06-17T18:12:27Z",
  "published" : "2026-06-17T18:12:27Z",
  "aliases" : [ "CVE-2026-5079" ],
  "summary" : "Multer vulnerable to Denial of Service via deeply nested field names",
  "details" : "### Impact\n\nMulter is vulnerable to a Denial of Service (DoS) via deeply nested field names in multipart form data. The `append-field` dependency parses bracket notation in field names (e.g., `a[b][c]`) 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.\n\n### Patches\n\nUsers should upgrade to `2.2.0` and configure `limits.fieldNestingDepth` to the minimum depth their application requires.\n\n### Workarounds\n\nSet `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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "multer"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.0.0"
      }, {
        "fixed" : "2.2.0"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "multer"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.0.0-alpha.1"
      }, {
        "fixed" : "3.0.0-alpha.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24j"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-5079"
  }, {
    "type" : "WEB",
    "url" : "https://cna.openjsf.org/security-advisories.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/expressjs/multer"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-17T18:12:27Z",
    "nvd_published_at" : "2026-06-15T14:16:37Z"
  }
}