Vulnerability-Lookup

CVE-2026-82333 (GCVE-0-2026-82333)

Vulnerability from cvelistv5 – Published: 2026-08-28 20:12 – Updated: 2026-08-31 18:39

Title

multer vulnerable to Denial of Service via oversized array index in field names

Summary

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.

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-31 18:39 UTC

CWE

CWE-400 - Uncontrolled Resource Consumption

Assigner

openjs redhat root

References

2 references

URL	Tags
https://github.com/expressjs/multer/security/advi…
https://cna.openjsf.org/security-advisories.html

Impacted products

1 product

Vendor	Product	Version	CPE status
multer	multer	Affected: 0 , < 2.3.0 (semver) Unaffected: 2.3.0 (semver)	guessed

Credits

O4FDev UlisesGascon arpitjain099

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-82333

Vulnerability from fkie_nvd - Published: 2026-08-28 22:16 - Updated: 2026-09-02 14:45

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	ce714d77-add3-4f53-aff5-83d477b104bb	https://cna.openjsf.org/security-advisories.html	Vendor Advisory
	ce714d77-add3-4f53-aff5-83d477b104bb	https://github.com/expressjs/multer/security/advisories/GHSA-535w-7cp7-47q4	Vendor Advisory

Impacted products

	Vendor	Product	Version
	expressjs	multer	*

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:npm/multer",
          "product": "multer",
          "vendor": "multer",
          "versions": [
            {
              "lessThan": "2.3.0",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
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            {
              "status": "unaffected",
              "version": "2.3.0",
              "versionType": "semver"
            }
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      "lang": "en",
      "value": "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\u0027s 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."
    }
  ],
  "id": "CVE-2026-82333",
  "lastModified": "2026-09-02T14:45:57.747",
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GHSA-535W-7CP7-47Q4

Vulnerability from github – Published: 2026-09-08 21:28 – Updated: 2026-09-08 21:28

Summary

multer vulnerable to Denial of Service via oversized array index in field names

Details

Impact

multer is vulnerable to a Denial of Service (DoS) via a crafted array index in multipart field names. The append-field dependency parses bracket notation in field names, and a large numeric index such as items[4294967294] forces allocation of a maximum-length sparse array. A following field with a non-numeric key on the same base then converts that array to an object by iterating its full length, which consumes CPU synchronously and leaves the process unable to handle other requests. A single HTTP request with a crafted multipart body is sufficient to exploit this, and it affects multer 1.x and 2.x.

Patches

Users should upgrade to 2.3.0 and configure limits.fieldArrayIndexLimit to the minimum array index their application requires.

Workarounds

None.

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "multer"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-82333"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-08T21:28:43Z",
    "nvd_published_at": "2026-08-28T22:16:57Z",
    "severity": "HIGH"
  },
  "details": "### Impact\n\nmulter is vulnerable to a Denial of Service (DoS) via a crafted array index in multipart field names. The `append-field` dependency parses bracket notation in field names, and a large numeric index such as `items[4294967294]` forces allocation of a maximum-length sparse array. A following field with a non-numeric key on the same base then converts that array to an object by iterating its full length, which consumes CPU synchronously and leaves the process unable to handle other requests. A single HTTP request with a crafted multipart body is sufficient to exploit this, and it affects multer 1.x and 2.x.\n\n### Patches\n\nUsers should upgrade to `2.3.0` and configure `limits.fieldArrayIndexLimit` to the minimum array index their application requires.\n\n### Workarounds\n\nNone.",
  "id": "GHSA-535w-7cp7-47q4",
  "modified": "2026-09-08T21:28:43Z",
  "published": "2026-09-08T21:28:43Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/expressjs/multer/security/advisories/GHSA-535w-7cp7-47q4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-82333"
    },
    {
      "type": "WEB",
      "url": "https://github.com/expressjs/multer/pull/1438"
    },
    {
      "type": "WEB",
      "url": "https://github.com/expressjs/multer/commit/73c1759fa93b87366bc6dbd7abe1b80ddff7d27c"
    },
    {
      "type": "WEB",
      "url": "https://cna.openjsf.org/security-advisories.html"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/expressjs/multer"
    },
    {
      "type": "WEB",
      "url": "https://github.com/expressjs/multer/releases/tag/v2.3.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "multer vulnerable to Denial of Service via oversized array index in field names"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-82333 (GCVE-0-2026-82333)

FKIE_CVE-2026-82333

GHSA-535W-7CP7-47Q4

Impact

Patches

Workarounds

Tags

Sightings

Nomenclature

Related by attack behaviour