Socket.IO: Engine.IO Polling Transport Connection Exhaustion

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Summary

CVECVE-2026-59725
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-08 16:16:33 UTC
Updated2026-07-08 18:16:34 UTC
DescriptionSocket.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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-404 | CWE-404 CWE-404: Improper Resource Shutdown or Release

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Socketio Socket.io affected >= 4.1.0, < 6.6.7 Not specified

References

ReferenceSourceLinkTags
github.com/socketio/socket.io/releases/tag/[email protected] [email protected] github.com
github.com/socketio/socket.io/security/advisories/GHSA-r635-g3xr-vw7x [email protected] github.com
github.com/socketio/socket.io/commit/fc11285e14964c2132d122164bf130c355f... [email protected] github.com
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