---
id: CVE-2026-102599
title: >-
  Socket.IO enables bidirectional and low-latency communication for every
  platform
summary: >-
  Socket.IO enables bidirectional and low-latency communication for every
  platform. From Engine.IO 6.6.0 until 6.6.10, a transport upgrade can
  independently derive an Engine.IO protocol revision from the upgrade request
  instead of enforcin…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-248
vendor: engine.io
product: engine.io
affected:
  - 'engine.io >= 6.6.0, < 6.6.10'
patched:
  - engine.io 6.6.10
published: '2026-10-13'
updated: '2026-10-17'
sourceUpdated: '2026-10-17T02:17:08.197'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102599'
references:
  - url: >-
      https://github.com/socketio/socket.io/commit/86db1fc3db2cd315a065d64c4e48918ccf9b4729
    label: security-advisories@github.com
  - url: 'https://github.com/socketio/socket.io/releases/tag/engine.io@6.6.10'
    label: security-advisories@github.com
  - url: >-
      https://github.com/socketio/socket.io/security/advisories/GHSA-2gc4-cqfq-p2gv
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-2gc4-cqfq-p2gv'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-102599.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-102599'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2551068'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-102599'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102599'
tags:
  - nvd
  - ghsa
  - npm
  - csaf
  - vex
  - red-hat
  - cve.org
epss: 0.00576
epssPercentile: 0.47302
aliases:
  - GHSA-2gc4-cqfq-p2gv
ecosystem: npm
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-17T00:39:37.132946Z'
ingestedAt: '2026-09-29T23:52:50.539Z'
---

## Overview

Socket.IO enables bidirectional and low-latency communication for every platform. From Engine.IO 6.6.0 until 6.6.10, a transport upgrade can independently derive an Engine.IO protocol revision from the upgrade request instead of enforcing the revision stored on the existing session. A malicious client can establish a valid session and send an upgrade request with a different or omitted EIO query parameter, attaching a transport with incompatible parser and heartbeat behavior. A crafted heartbeat packet can then trigger an uncaught exception and terminate the Node.js process, including when Engine.IO v3 compatibility is disabled because an omitted EIO value is interpreted as revision 3 on the affected path. This issue is fixed in Engine.IO 6.6.10.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-102599)

Affected packages:

- `engine.io >= 6.6.0, < 6.6.10`

Patched in:

- `engine.io 6.6.10`

Source: https://github.com/advisories/GHSA-2gc4-cqfq-p2gv

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat Hardened Images · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat Hardened Images · updated 2026-10-19 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-102599.json)