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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.

PUBLISHED Reserved 2026-07-06 | Published 2026-07-08 | Updated 2026-07-08 | Assigner GitHub_M




HIGH: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem types

CWE-404: Improper Resource Shutdown or Release

Product status

>= 4.1.0, < 6.6.7
affected

References

github.com/...ket.io/security/advisories/GHSA-r635-g3xr-vw7x

github.com/...ommit/fc11285e14964c2132d122164bf130c355f60671

github.com/socketio/socket.io/releases/tag/engine.io@6.6.7

cve.org (CVE-2026-59725)

nvd.nist.gov (CVE-2026-59725)

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