Vulnerability-Lookup

GHSA-WFPM-5GCM-94CG

Vulnerability from github – Published: 2026-10-05 23:44 – Updated: 2026-10-05 23:44

Summary

Socket.IO: Prototype Pollution via Unsafe Client Session Lookup

Details

Impact

This is a prototype pollution / improper client lookup vulnerability in @socket.io/cluster-engine.

Servers using @socket.io/cluster-engine may be impacted when attacker-controlled session IDs are processed in clustered deployments. A malicious client could use special property names such as __proto__, constructor, or other inherited object keys as a session identifier, causing the server to read properties from the object prototype chain instead of only real connected clients.

The impact is denial of service through process crash.

Applications not using @socket.io/cluster-engine are not affected by this specific issue.

Affected versions:

@socket.io/cluster-engine@0.1.0

Patches

The issue was fixed in:

@socket.io/cluster-engine@0.1.1

Workarounds

If upgrading immediately is not possible, users can reduce exposure by:

Rejecting or sanitizing suspicious session IDs before they reach the cluster engine.
Running the cluster engine behind trusted infrastructure that prevents arbitrary clients from crafting raw Engine.IO session-related requests.

These workarounds are defense-in-depth only. Upgrading to a patched version is recommended.

Severity

7.5 (High)


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

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@socket.io/cluster-engine"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.1.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-102600"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-05T23:44:21Z",
    "nvd_published_at": "2026-09-29T16:17:06Z",
    "severity": "HIGH"
  },
  "details": "### Impact\n\nThis is a **prototype pollution / improper client lookup** vulnerability in `@socket.io/cluster-engine`.\n\nServers using `@socket.io/cluster-engine` may be impacted when attacker-controlled session IDs are processed in clustered deployments. A malicious client could use special property names such as `__proto__`, `constructor`, or other inherited object keys as a session identifier, causing the server to read properties from the object prototype chain instead of only real connected clients.\n\nThe impact is **denial of service** through process crash.\n\nApplications not using `@socket.io/cluster-engine` are not affected by this specific issue.\n\nAffected versions:\n\n*  `@socket.io/cluster-engine@0.1.0`\n\n### Patches\n\nThe issue was fixed in:\n\n*  `@socket.io/cluster-engine@0.1.1`\n\n### Workarounds\n\nIf upgrading immediately is not possible, users can reduce exposure by:\n\n- Rejecting or sanitizing suspicious session IDs before they reach the cluster engine.\n- Running the cluster engine behind trusted infrastructure that prevents arbitrary clients from crafting raw Engine.IO session-related requests.\n\nThese workarounds are defense-in-depth only. Upgrading to a patched version is recommended.",
  "id": "GHSA-wfpm-5gcm-94cg",
  "modified": "2026-10-05T23:44:21Z",
  "published": "2026-10-05T23:44:21Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/socketio/socket.io/security/advisories/GHSA-wfpm-5gcm-94cg"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-102600"
    },
    {
      "type": "WEB",
      "url": "https://github.com/socketio/socket.io/commit/830e3642ebb8dc3784eb749b0a004fe2b932b429"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/socketio/socket.io"
    },
    {
      "type": "WEB",
      "url": "https://github.com/socketio/socket.io/releases/tag/@socket.io/cluster-engine@0.1.1"
    }
  ],
  "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: Prototype Pollution via Unsafe Client Session Lookup"
}

CVE-2026-102600 (GCVE-0-2026-102600)

Vulnerability from cvelistv5 – Published: 2026-09-29 15:23 – Updated: 2026-09-29 16:28

Title

Socket.IO: Prototype Pollution via Unsafe Client Session Lookup

Summary

Socket.IO enables bidirectional and low-latency communication for every platform. Prior to 0.1.1, @socket.io/cluster-engine uses inherited object properties when looking up attacker-controlled session IDs in clustered deployments. Special property names such as __proto__ or constructor can resolve through the object prototype chain instead of identifying an actual connected client, causing the Node.js process to crash and resulting in denial of service. Applications that do not use @socket.io/cluster-engine are not affected. This issue is fixed in version 0.1.1.

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 2026-09-29 16:27 UTC

CWE

CWE-20 - Improper Input Validation
CWE-1321 - Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Assigner

GitHub_M mitre root Scorecard

References

3 references

URL	Tags
https://github.com/socketio/socket.io/security/ad…	x_refsource_CONFIRM
https://github.com/socketio/socket.io/commit/830e…	x_refsource_MISC
https://github.com/socketio/socket.io/releases/ta…	x_refsource_MISC

Impacted products

2 products

Vendor	Product	Version
socketio	socket.io	Affected: < 0.1.1
@socket.io	cluster-engine	Affected: < 0.1.1

Show details on NVD website

JSON

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        "metrics": [
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                "id": "CVE-2026-102600",
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                  },
                  {
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                "role": "CISA Coordinator",
                "timestamp": "2026-09-29T16:27:29.573677Z",
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          "shortName": "CISA-ADP"
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    "cna": {
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          "value": "Socket.IO enables bidirectional and low-latency communication for every platform. Prior to 0.1.1, @socket.io/cluster-engine uses inherited object properties when looking up attacker-controlled session IDs in clustered deployments. Special property names such as __proto__ or constructor can resolve through the object prototype chain instead of identifying an actual connected client, causing the Node.js process to crash and resulting in denial of service. Applications that do not use @socket.io/cluster-engine are not affected. This issue is fixed in version 0.1.1."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
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            "confidentialityImpact": "NONE",
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              "lang": "en",
              "type": "CWE"
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      "providerMetadata": {
        "dateUpdated": "2026-09-29T15:23:15.857Z",
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  "cveMetadata": {
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    "datePublished": "2026-09-29T15:23:15.857Z",
    "dateReserved": "2026-09-29T14:18:02.920Z",
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  "dataType": "CVE_RECORD",
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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.

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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