CVE-2026-102600: @socket.io/cluster engine Prototype Pollution Vulnerability
HIGHCVE-2026-102600 is a HIGH (CVSS 7.5) prototype pollution vulnerability (CWE-20: Improper Input Validation) affecting @socket.io/cluster engine libraries in the npm ecosystem. The issue involves prototype pollution via unsafe client session lookup. Remediation is available by upgrading affected packages to version 0.1.1.
CVE-2026-102600 at a Glance
Security Impact
CVSS: 7.5
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
How to Fix CVE-2026-102600
To remediate this vulnerability, upgrade all affected @socket.io/cluster engine dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
npm install @socket.io/cluster-engine@0.1.1Run the following command in your project directory to verify that all resolved dependencies use the patched release:
npm ls @socket.io/cluster-engineHow to Check if You Are Affected
To determine whether your Node.js application is affected by CVE-2026-102600, inspect your project dependencies using npm:
npm ls @socket.io/cluster-engineAnalyze the terminal output to locate any version of @socket.io/cluster engine in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.1.1), your application is affected.
Note: The npm ls @socket.io/cluster-engine command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In @socket.io/cluster engine, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-102600 Affected @socket.io/cluster engine Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
@socket.io/cluster-engine
|
npm |
< 0.1.1
|
0.1.1
|
References
Frequently Asked Questions
What is CVE-2026-102600?
Which @socket.io/cluster engine versions are affected?
What version fixes CVE-2026-102600?
Is @socket.io/cluster-engine affected?
What is the CVSS score of CVE-2026-102600?
What CWE is associated with CVE-2026-102600?
How can I check npm dependencies for CVE-2026-102600?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-wfpm-5gcm-94cg",
"modified" : "2026-10-05T23:44:21Z",
"published" : "2026-10-05T23:44:21Z",
"aliases" : [ "CVE-2026-102600" ],
"summary" : "Socket.IO: Prototype Pollution via Unsafe Client Session Lookup",
"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.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "npm",
"name" : "@socket.io/cluster-engine"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "0.1.1"
} ]
} ]
} ],
"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"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-20" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2026-10-05T23:44:21Z",
"nvd_published_at" : "2026-09-29T16:17:06Z"
}
}