Vulnerability-Lookup

GHSA-GR94-W7QR-F4J3

Vulnerability from github – Published: 2026-08-31 21:28 – Updated: 2026-08-31 21:28

Summary

Socket.IO: Engine.IO WebTransport SID DoS

Details

Impact

Engine.IO servers with WebTransport enabled are vulnerable to a remotely triggerable denial of service.

A malicious unauthenticated client can send a crafted WebTransport upgrade request containing a specially chosen session ID, such as __proto__. Because the session ID lookup did not properly verify that the key was an own property of the clients object, the lookup could resolve to an inherited prototype property instead of a valid Engine.IO client.

This can cause a TypeError during WebTransport upgrade handling. Since the failure occurs in an asynchronous context, it may result in an unhandled Promise rejection and terminate the Node.js process on affected Node.js versions/configurations.

Successful exploitation can allow an unauthenticated remote attacker to crash the server process and cause denial of service. Under a process supervisor, repeated exploitation may cause crash loops.

Affected configurations are limited to deployments where WebTransport support is enabled. WebTransport is not enabled by default.

Affected versions:

engine.io >= 6.5.0 < 6.6.7

Patches

The issue was fixed in:

engine.io 6.6.7

Users should upgrade to engine.io@6.6.7 or later.

If using Socket.IO packages that depend on Engine.IO, users should update to a Socket.IO release that includes the patched Engine.IO version.

Workarounds

If upgrading immediately is not possible, affected users can mitigate the issue by disabling WebTransport support.

WebTransport is opt-in, so servers should ensure that webtransport is not included in the enabled transports list.

For example, use only the default HTTP long-polling and WebSocket transports:

const engine = new Server({
  transports: ["polling", "websocket"],
});

Additional operational mitigations may include:

Restricting access to WebTransport endpoints at the reverse proxy or HTTP/3 layer.
Disabling HTTP/3/WebTransport support until the patched version can be deployed.
Running the service under a supervisor as a partial availability mitigation, though this does not prevent repeated crash attempts.

References

Fix commit: https://github.com/socketio/socket.io/commit/1fa1f46cd420ac5b57bb4c04c959b58f3c79158c
Engine.IO changelog entry for 6.6.7: https://github.com/socketio/socket.io/blob/main/packages/engine.io/CHANGELOG.md#667-2026-04-27
Engine.IO package: https://www.npmjs.com/package/engine.io
Socket.IO repository: https://github.com/socketio/socket.io

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": "engine.io"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.5.0"
            },
            {
              "fixed": "6.6.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-59724"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-31T21:28:12Z",
    "nvd_published_at": "2026-07-08T16:16:32Z",
    "severity": "HIGH"
  },
  "details": "### Impact\n\nEngine.IO servers with **WebTransport enabled** are vulnerable to a remotely triggerable denial of service.\n\nA malicious unauthenticated client can send a crafted WebTransport upgrade request containing a specially chosen session ID, such as `__proto__`. Because the session ID lookup did not properly verify that the key was an own property of the clients object, the lookup could resolve to an inherited prototype property instead of a valid Engine.IO client.\n\nThis can cause a `TypeError` during WebTransport upgrade handling. Since the failure occurs in an asynchronous context, it may result in an unhandled Promise rejection and terminate the Node.js process on affected Node.js versions/configurations.\n\nSuccessful exploitation can allow an unauthenticated remote attacker to crash the server process and cause denial of service. Under a process supervisor, repeated exploitation may cause crash loops.\n\nAffected configurations are limited to deployments where WebTransport support is enabled. WebTransport is not enabled by default.\n\nAffected versions:\n\n- `engine.io \u003e= 6.5.0 \u003c 6.6.7`\n\n## Patches\n\nThe issue was fixed in:\n\n- **engine.io 6.6.7**\n\nUsers should upgrade to `engine.io@6.6.7` or later.\n\nIf using Socket.IO packages that depend on Engine.IO, users should update to a Socket.IO release that includes the patched Engine.IO version.\n\n### Workarounds\n\nIf upgrading immediately is not possible, affected users can mitigate the issue by disabling WebTransport support.\n\nWebTransport is opt-in, so servers should ensure that `webtransport` is not included in the enabled transports list.\n\nFor example, use only the default HTTP long-polling and WebSocket transports:\n\n```js\nconst engine = new Server({\n  transports: [\"polling\", \"websocket\"],\n});\n```\n\nAdditional operational mitigations may include:\n\n- Restricting access to WebTransport endpoints at the reverse proxy or HTTP/3 layer.\n- Disabling HTTP/3/WebTransport support until the patched version can be deployed.\n- Running the service under a supervisor as a partial availability mitigation, though this does not prevent repeated crash attempts.\n\n### References\n\n- Fix commit: https://github.com/socketio/socket.io/commit/1fa1f46cd420ac5b57bb4c04c959b58f3c79158c\n- Engine.IO changelog entry for `6.6.7`: https://github.com/socketio/socket.io/blob/main/packages/engine.io/CHANGELOG.md#667-2026-04-27\n- Engine.IO package: https://www.npmjs.com/package/engine.io\n- Socket.IO repository: https://github.com/socketio/socket.io",
  "id": "GHSA-gr94-w7qr-f4j3",
  "modified": "2026-08-31T21:28:12Z",
  "published": "2026-08-31T21:28:12Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/socketio/socket.io/security/advisories/GHSA-gr94-w7qr-f4j3"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59724"
    },
    {
      "type": "WEB",
      "url": "https://github.com/socketio/socket.io/commit/1fa1f46cd420ac5b57bb4c04c959b58f3c79158c"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/socketio/socket.io"
    },
    {
      "type": "WEB",
      "url": "https://github.com/socketio/socket.io/releases/tag/engine.io@6.6.7"
    }
  ],
  "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": "Socket.IO: Engine.IO WebTransport SID DoS"
}

CVE-2026-59724 (GCVE-0-2026-59724)

Vulnerability from cvelistv5 – Published: 2026-07-08 15:35 – Updated: 2026-07-08 19:41

Title

Socket.IO: Engine.IO WebTransport SID DoS

Summary

Socket.IO enables bidirectional and low-latency communication for every platform. From 6.5.0 before 6.6.7, Engine.IO servers with WebTransport enabled can resolve a crafted session ID such as __proto__ through an inherited property of the clients object during WebTransport upgrade handling, causing a TypeError and denial of service. This issue is fixed in version 6.6.7.

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 2026-07-08 17:58 UTC

CWE

CWE-20 - Improper Input Validation

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/socketio/socket.io/security/ad…	x_refsource_CONFIRM
https://github.com/socketio/socket.io/commit/1fa1…	x_refsource_MISC
https://github.com/socketio/socket.io/releases/ta…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
socketio	socket.io	Affected: >= 6.5.0, < 6.6.7

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-59724",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-08T17:58:43.578991Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-08T19:41:18.905Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "socket.io",
          "vendor": "socketio",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 6.5.0, \u003c 6.6.7"
            }
          ]
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Socket.IO enables bidirectional and low-latency communication for every platform. From 6.5.0 before 6.6.7, Engine.IO servers with WebTransport enabled can resolve a crafted session ID such as __proto__ through an inherited property of the clients object during WebTransport upgrade handling, causing a TypeError and denial of service. This issue is fixed in version 6.6.7."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-20",
              "description": "CWE-20: Improper Input Validation",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-08T15:35:39.813Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/socketio/socket.io/security/advisories/GHSA-gr94-w7qr-f4j3",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/socketio/socket.io/security/advisories/GHSA-gr94-w7qr-f4j3"
        },
        {
          "name": "https://github.com/socketio/socket.io/commit/1fa1f46cd420ac5b57bb4c04c959b58f3c79158c",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/socketio/socket.io/commit/1fa1f46cd420ac5b57bb4c04c959b58f3c79158c"
        },
        {
          "name": "https://github.com/socketio/socket.io/releases/tag/engine.io@6.6.7",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/socketio/socket.io/releases/tag/engine.io@6.6.7"
        }
      ],
      "source": {
        "advisory": "GHSA-gr94-w7qr-f4j3",
        "discovery": "UNKNOWN"
      },
      "title": "Socket.IO: Engine.IO WebTransport SID DoS"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-59724",
    "datePublished": "2026-07-08T15:35:39.813Z",
    "dateReserved": "2026-07-06T15:34:16.916Z",
    "dateUpdated": "2026-07-08T19:41:18.905Z",
    "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.

Action not permitted

GHSA-GR94-W7QR-F4J3

Impact

Patches

Workarounds

References

CVE-2026-59724 (GCVE-0-2026-59724)

Tags

Sightings

Nomenclature