High 7.5Published Jul 8, 2026

CVE-2026-59725Socket.IO: Engine.IO Polling Transport Connection Exhaustion

Updated under an hour ago (2026-10-19 08:23 UTC)

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It affects socketio engine.io and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for socketio engine.io

Exploited in the last 30 days

Socket.IO enables bidirectional and low-latency communication for every platform. From 4.1.0 before 6.6.7, Engine.IO protocol v4 polling transport does not properly close the HTTP response for invalid binary POST requests with Content-Type: application/octet-stream, allowing an unauthenticated attacker to exhaust server-side connections and sockets. This issue is fixed in version 6.6.7.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-404
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Oct 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

socketio engine.io socketio:engine.io (from the name)	from 4.1.0, < 6.6.7	CNA record
socket engine.io socket:engine.io	from 4.1.0 before 6.6.7	NVD

References

https://github.com/socketio/socket.io/security/advisories/GHSA-r635-g3xr-vw7xx-refsource-confirm, patch, vendor-advisory
https://github.com/socketio/socket.io/commit/fc11285e14964c2132d122164bf130c355f60671x-refsource-misc, patch
https://github.com/socketio/socket.io/releases/tag/engine.io@6.6.7x-refsource-misc, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.