Vulnerability-Lookup

GHSA-8HQ7-GGX2-CC6M

Vulnerability from github – Published: 2026-10-08 17:39 – Updated: 2026-10-08 17:39

Summary

msgpack5: Partial options disable prototype protection

Details

Impact

Passing an empty or partial options object disables the default protoAction: 'error' protection. A map containing a __proto__ key can then replace the prototype of the decoded object, potentially changing inherited properties or causing unexpected behavior in downstream code.

Only the decoded object's prototype is affected; this does not modify Object.prototype globally.

Patches

Options are now merged with secure defaults without modifying the caller's object. Unsupported protoAction values are rejected.

Workarounds

Explicitly set protoAction: 'error' whenever constructing a msgpack5 instance, and validate decoded values before use.

Severity

6.5 (Medium)


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

Show details on source website

JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "msgpack5"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-107301"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-08T17:39:57Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nPassing an empty or partial options object disables the default `protoAction: \u0027error\u0027` protection. A map containing a `__proto__` key can then replace the prototype of the decoded object, potentially changing inherited properties or causing unexpected behavior in downstream code.\n\nOnly the decoded object\u0027s prototype is affected; this does not modify `Object.prototype` globally.\n\n### Patches\n\nOptions are now merged with secure defaults without modifying the caller\u0027s object. Unsupported `protoAction` values are rejected.\n\n### Workarounds\n\nExplicitly set `protoAction: \u0027error\u0027` whenever constructing a msgpack5 instance, and validate decoded values before use.",
  "id": "GHSA-8hq7-ggx2-cc6m",
  "modified": "2026-10-08T17:39:57Z",
  "published": "2026-10-08T17:39:57Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mcollina/msgpack5/security/advisories/GHSA-8hq7-ggx2-cc6m"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mcollina/msgpack5/commit/20e82600ac9462e679c8a45e5723315f21e2c774"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mcollina/msgpack5"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mcollina/msgpack5/releases/tag/v6.1.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "msgpack5: Partial options disable prototype protection"
}

CVE-2026-107301 (GCVE-0-2026-107301)

Vulnerability from cvelistv5 – Published: 2026-10-08 17:13 – Updated: 2026-10-08 17:13

Title

msgpack5: Partial options disable prototype protection

Summary

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, constructing msgpack5 with an empty or partial options object disables the default protoAction: 'error' protection. A decoded map containing a __proto__ key can then replace the decoded object's prototype, potentially changing inherited properties or downstream behavior, although Object.prototype is not modified globally. This issue is fixed in version 6.1.0.

Severity

6.5 (Medium)


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

CWE

CWE-1321 - Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7581 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/mcollina/msgpack5/security/adv…	x_refsource_CONFIRM
https://github.com/mcollina/msgpack5/commit/20e82…	x_refsource_MISC
https://github.com/mcollina/msgpack5/releases/tag…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
mcollina	msgpack5	Affected: < 6.1.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "msgpack5",
          "vendor": "mcollina",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 6.1.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, constructing msgpack5 with an empty or partial options object disables the default protoAction: \u0027error\u0027 protection. A decoded map containing a __proto__ key can then replace the decoded object\u0027s prototype, potentially changing inherited properties or downstream behavior, although Object.prototype is not modified globally. This issue is fixed in version 6.1.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1321",
              "description": "CWE-1321: Improperly Controlled Modification of Object Prototype Attributes (\u0027Prototype Pollution\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-08T17:13:00.613Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/mcollina/msgpack5/security/advisories/GHSA-8hq7-ggx2-cc6m",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/mcollina/msgpack5/security/advisories/GHSA-8hq7-ggx2-cc6m"
        },
        {
          "name": "https://github.com/mcollina/msgpack5/commit/20e82600ac9462e679c8a45e5723315f21e2c774",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mcollina/msgpack5/commit/20e82600ac9462e679c8a45e5723315f21e2c774"
        },
        {
          "name": "https://github.com/mcollina/msgpack5/releases/tag/v6.1.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mcollina/msgpack5/releases/tag/v6.1.0"
        }
      ],
      "source": {
        "advisory": "GHSA-8hq7-ggx2-cc6m",
        "discovery": "UNKNOWN"
      },
      "title": "msgpack5: Partial options disable prototype protection"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-107301",
    "datePublished": "2026-10-08T17:13:00.613Z",
    "dateReserved": "2026-10-07T15:53:23.587Z",
    "dateUpdated": "2026-10-08T17:13:00.613Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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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.
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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.

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.
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