Vulnerability-Lookup

GHSA-QVFW-J98X-7Q72

Vulnerability from github – Published: 2026-09-08 21:29 – Updated: 2026-09-08 21:29

Summary

multer vulnerable to file size limit bypass via async fileFilter race condition

Details

Impact

When multer is configured with an asynchronous fileFilter, the limits.fileSize limit can be bypassed. The 'limit' event is registered inside the async fileFilter callback, so if a file exceeds limits.fileSize before that callback runs, the event is missed and the oversized upload is accepted instead of being rejected with a LIMIT_FILE_SIZE error. Applications that rely on limits.fileSize to reject oversized uploads are affected on all upload methods (.single(), .array(), .fields(), .any()). Uploads using a synchronous fileFilter are not affected.

Patches

Users should upgrade to 2.3.0.

Workarounds

Use a synchronous fileFilter, or validate the uploaded file size after the upload completes.

Severity

3.7 (Low)


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

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JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "multer"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
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              "fixed": "2.3.0"
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          "type": "ECOSYSTEM"
        }
      ]
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  ],
  "aliases": [
    "CVE-2026-77063"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-362"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-08T21:29:42Z",
    "nvd_published_at": "2026-08-28T22:16:53Z",
    "severity": "LOW"
  },
  "details": "### Impact\n\nWhen `multer` is configured with an asynchronous `fileFilter`, the `limits.fileSize` limit can be bypassed. The `\u0027limit\u0027` event is registered inside the async `fileFilter` callback, so if a file exceeds `limits.fileSize` before that callback runs, the event is missed and the oversized upload is accepted instead of being rejected with a `LIMIT_FILE_SIZE` error. Applications that rely on `limits.fileSize` to reject oversized uploads are affected on all upload methods (`.single()`, `.array()`, `.fields()`, `.any()`). Uploads using a synchronous `fileFilter` are not affected.\n\n### Patches\n\nUsers should upgrade to `2.3.0`.\n\n### Workarounds\n\nUse a synchronous `fileFilter`, or validate the uploaded file size after the upload completes.",
  "id": "GHSA-qvfw-j98x-7q72",
  "modified": "2026-09-08T21:29:42Z",
  "published": "2026-09-08T21:29:42Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/expressjs/multer/security/advisories/GHSA-qvfw-j98x-7q72"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-77063"
    },
    {
      "type": "WEB",
      "url": "https://github.com/expressjs/multer/commit/ab6aeae650328cf31799dcfa4c3e116ba8faaacc"
    },
    {
      "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:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "multer vulnerable to file size limit bypass via async fileFilter race condition"
}

CVE-2026-77063 (GCVE-0-2026-77063)

Vulnerability from cvelistv5 – Published: 2026-08-28 19:54 – Updated: 2026-08-31 18:40

Title

multer vulnerable to file size limit bypass via async fileFilter race condition

Summary

multer is a middleware for handling multipart/form-data in Node.js. When an application uses an asynchronous fileFilter together with the fileSize limit, a race condition in multer's file stream handling can allow a file that exceeds the configured size limit to bypass the size-limit rejection. All versions before 2.3.0 are affected. The impact is limited because the underlying multipart parser still truncates the stream at the size limit, so this is a bypass of the limit rejection rather than uncontrolled resource consumption. The issue is fixed in multer 2.3.0. Upgrade to multer 2.3.0 to remediate.

Severity

3.7 (Low)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-31 18:40 UTC

CWE

CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

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
multer	multer	Affected: 0 , < 2.3.0 (semver) Unaffected: 2.3.0 (semver)

Credits

ThinkerHao bjohansebas UlisesGascon

Show details on NVD website

JSON

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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

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