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Socket.IO: Engine.IO Protocol Revision Mismatch DoS

Type: advisorySource: Official CVE List1 source record

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.

Announced Source revision 1
Original source ↗

CVE-2026-102599

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-102599

socket.io

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "vendor": "socketio",
    "product": "socket.io",
    "versions": [
      {
        "status": "affected",
        "version": ">= 6.6.0, < 6.6.10"
      }
    ]
  }
]
Related CVEs
CVE-2026-102599

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Linked CVE context

These ratings describe the referenced vulnerabilities and products. They are not a severity rating for every application using this dependency.

CVE-2026-102599 · High

engine.io

Event
#34512 · Revision 1
Added to Heist Feed
Publisher date
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