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

CVSS 7.5 · High EPSS 0.35% · P28

Possible ATT&CK Techniques 1AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProductVersion RangeStatus
socketiosocket.io>= 4.1.0, < 6.6.7affected
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I. Basic Information for CVE-2026-59725

Vulnerability Information
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Vulnerability Title
Socket.IO: Engine.IO Polling Transport Connection Exhaustion
Source: NVD (National Vulnerability Database)
Vulnerability Description
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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
不恰当的资源关闭或释放
Source: NVD (National Vulnerability Database)

Affected Products

VendorProductAffected VersionsCPESubscribe
socketiosocket.io >= 4.1.0, < 6.6.7 -

II. Public POCs for CVE-2026-59725

#POC DescriptionSource LinkShenlong Link
AI-Generated POCVerified env Premium
Qwen3.6-35B-A3B · 8379 chars
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III. Intelligence Information for CVE-2026-59725

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Patches & Fixes for CVE-2026-59725 (1)

Vendor Advisories for CVE-2026-59725 (1)

Vendor Pages for CVE-2026-59725 (1)

IV. Related Vulnerabilities

Same product: socket.io
Same vendor: socketio
Same weakness: CWE-404

V. Comments for CVE-2026-59725

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