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Fencer Vulns
high 7.5

CVE-2026-59725 json

Socket.IO: Engine.IO Polling Transport Connection Exhaustion

published 2026-07-08 4 mo ago modified 2026-10-25 14 d ago also GHSA-r635-g3xr-vw7x , EUVD-2026-42313

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm engine.io 6.6.7
  • socket engine.io 6.6.7
  • dotnet8.0 hummingbird 1 8.0.129-2.hum1
  • dotnet-sdk-8.0 hummingbird 1 8.0.129-2.hum1
  • dotnet-sdk-dbg-8.0 hummingbird 1 8.0.129-2.hum1
  • dotnet-templates-8.0 hummingbird 1 8.0.129-2.hum1
  • dotnet-sdk-8.0-source-built-artifacts hummingbird 1 8.0.129-2.hum1
  • dotnet8.0 hummingbird 1 8.0.128-1.1.hum1
  • dotnet-sdk-8.0 hummingbird 1 8.0.128-1.1.hum1
  • dotnet-hostfxr-8.0 hummingbird 1 8.0.28-1.1.hum1

red hat advisories RHSA-2026:42986RHSA-2026:37577

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-59725 updated cvss 7.5

socket.io: engine.io: Socket.IO: Denial of Service via invalid binary POST requests

  • Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/disk-image-cuda-rhel9
    affected: no fix available, no fix planned “Will not fix”
  • Red Hat Hardened Images dotnet8.0 8.0.129-2.hum1, dotnet8.0 8.0.128-1.1.hum1, dotnet-sdk-8.0 8.0.129-2.hum1, dotnet-sdk-8.0 8.0.128-1.1.hum1, dotnet-sdk-dbg-8.0 8.0.129-2.hum1, dotnet-hostfxr-8.0 8.0.28-1.1.hum1, +12 more
    fixed: vendor fix RHSA-2026:37577
  • Red Hat Hardened Images dotnet-hostfxr-8.0 8.0.29-2.hum1, dotnet-runtime-8.0 8.0.29-2.hum1, aspnetcore-runtime-8.0 8.0.29-2.hum1, dotnet-runtime-dbg-8.0 8.0.29-2.hum1, dotnet-apphost-pack-8.0 8.0.29-2.hum1, dotnet-targeting-pack-8.0 8.0.29-2.hum1, +2 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.64% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
npm engine.io
>=4.1.0, <6.6.7
6.6.7

Affected products

  • socketio engine.io

Classification

Weakness
  • CWE-404 Improper Resource Shutdown or Release

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.