Vulnerability-Lookup

GHSA-8HQ9-PHH3-P2WP

Vulnerability from github – Published: 2026-03-17 16:17 – Updated: 2026-03-19 19:01

Summary

Elysia Cookie Value Prototype Pollution

Details

Impact

Elysia cookie can be overridden by prototype pollution , eg. __proto__

Sending cookie with the follows name can override cookie value:

__proto__=%7B%22injected%22%3A%22polluted%22%7D

Patches

Patched by 1.4.27

Workarounds

Use t.Cookie validation to enforce validation value
Prevent iterable over cookie if possible

Severity

6.5 (Medium)


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

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JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "elysia"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.4.27"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-31865"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-17T16:17:41Z",
    "nvd_published_at": "2026-03-18T04:17:19Z",
    "severity": "MODERATE"
  },
  "details": "### Impact\nElysia cookie can be overridden by prototype pollution , eg. `__proto__`\n\nSending cookie with the follows name can override cookie value:\n```bash\n__proto__=%7B%22injected%22%3A%22polluted%22%7D\n```\n\n### Patches\nPatched by 1.4.27\n\n### Workarounds\n1. Use t.Cookie validation to enforce validation value\n2. Prevent iterable over cookie if possible",
  "id": "GHSA-8hq9-phh3-p2wp",
  "modified": "2026-03-19T19:01:12Z",
  "published": "2026-03-17T16:17:41Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/elysiajs/elysia/security/advisories/GHSA-8hq9-phh3-p2wp"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31865"
    },
    {
      "type": "WEB",
      "url": "https://github.com/elysiajs/elysia/commit/e9d6b1743fa7368ef942dce181f6a089757f6aab"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/elysiajs/elysia"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Elysia Cookie Value Prototype Pollution"
}

CVE-2026-31865 (GCVE-0-2026-31865)

Vulnerability from cvelistv5 – Published: 2026-03-18 02:50 – Updated: 2026-03-18 18:39

Title

Elysia Cookie Value Prototype Pollution

Summary

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation, and client-server communication. Prior to version 1.4.27, an Elysia cookie can be overridden by prototype pollution , eg. `__proto__`. This issue is patched in 1.4.27. As a workaround, use t.Cookie validation to enforce validation value and/or prevent iterable over cookie if possible.

Severity

6.5 (Medium)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-03-18 18:36 UTC

CWE

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

Assigner

GitHub_M mitre root

References

2 references

URL	Tags
https://github.com/elysiajs/elysia/security/advis…	x_refsource_CONFIRM
https://github.com/elysiajs/elysia/commit/e9d6b17…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
elysiajs	elysia	Affected: < 1.4.27

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-31865",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-03-18T18:36:47.933361Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-03-18T18:39:09.024Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "elysia",
          "vendor": "elysiajs",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.4.27"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation, and client-server communication. Prior to version 1.4.27, an Elysia cookie can be overridden by prototype pollution , eg. `__proto__`. This issue is patched in 1.4.27. As a workaround, use t.Cookie validation to enforce validation value and/or prevent iterable over cookie if possible."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
            "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": "2026-03-18T02:50:55.403Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/elysiajs/elysia/security/advisories/GHSA-8hq9-phh3-p2wp",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/elysiajs/elysia/security/advisories/GHSA-8hq9-phh3-p2wp"
        },
        {
          "name": "https://github.com/elysiajs/elysia/commit/e9d6b1743fa7368ef942dce181f6a089757f6aab",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/elysiajs/elysia/commit/e9d6b1743fa7368ef942dce181f6a089757f6aab"
        }
      ],
      "source": {
        "advisory": "GHSA-8hq9-phh3-p2wp",
        "discovery": "UNKNOWN"
      },
      "title": "Elysia Cookie Value Prototype Pollution"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-31865",
    "datePublished": "2026-03-18T02:50:55.403Z",
    "dateReserved": "2026-03-09T19:02:25.013Z",
    "dateUpdated": "2026-03-18T18:39:09.024Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.