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CVE-2026-102599

CVE-2026-102599 · Socket.IO: Engine.IO Protocol Revision Mismatch DoS

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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.

CVSS 7.5 · High · EPSS 0.6% · Fix available

Published
Updated

Stack: node

Affected products and versions

  • socket.io

    Versions
    • >= 6.6.0, < 6.6.10: Affected

    No fix published

  • engine.io npm

    Affected ranges
    • SEMVER: ≥ 6.6.0, < 6.6.10

    Update to 6.6.10

Original sources

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