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TI-2026-42594 Aliases CVE-2026-59725GHSA-r635-g3xr-vw7x

Socket.IO: Engine.IO Polling Transport Connection Exhaustion

Priority MEDIUM 40CWE-404Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 1 fixed, 1 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-404.

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00636 50th percentileScored 2026-11-07
Fix Partial engine.io (socketio): 6.6.7engine.io (npm): 6.6.7Red Hat: 2 advisoriesRed Hat: 1 fixed, 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
socketioengine.io4.1.0 to before 6.6.76.6.7Patch availableCNA
—engine.io (npm)4.1.0 to before 6.6.76.6.7Patch availableGHSA-r635-g3xr-vw7x
  • engine.io Vendorsocketio Affected 4.1.0 to before 6.6.7 Fixed in 6.6.7 Patch available CNA
  • engine.io (npm) Vendor— Affected 4.1.0 to before 6.6.7 Fixed in 6.6.7 Patch available GHSA-r635-g3xr-vw7x

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:socket:engine.io:*:*:*:*:*:node.js:*:*4.1.0 to before 6.6.7Vulnerablesocketio
  • cpe:2.3:a:socket:engine.io:*:*:*:*:*:node.js:*:* Versions 4.1.0 to before 6.6.7 Vulnerable ·socketio

Remediation

  • Fix · CNA engine.io (socketio) Fixed in 6.6.7
  • Fix · GHSA-r635-g3xr-vw7x engine.io (npm) Fixed in 6.6.7 Advisory →

Red Hat 2 advisories

  • RHSA-2026:42986 Released 2026-07-21 · Red Hat rating Important
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images dotnet-sdk-8.0-8.0.129-2.hum1@aarch64, dotnet-sdk-8.0-8.0.129-2.hum1@x86_64, dotnet-sdk-8.0-source-built-artifacts-8.0.129-2.hum1@aarch64 +6
  • RHSA-2026:37577 Released 2026-07-10 · Red Hat rating Important
    Red Hat Hardened Images RPMs Security Update
    • Red Hat Hardened Images aspnetcore-runtime-8.0-8.0.28-1.1.hum1@aarch64, aspnetcore-runtime-8.0-8.0.28-1.1.hum1@x86_64, aspnetcore-runtime-dbg-8.0-8.0.28-1.1.hum1@aarch64 +22

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux AI (RHEL AI) 3AffectedNo fix yet
Red Hat Hardened ImagesFixed RHSA-2026:37577, RHSA-2026:42986
Not affected: 1 product
  • Red Hat Hardened Images

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-59725
  2. 2026-10-03 Alias added: GHSA-r635-g3xr-vw7x
  3. 2026-10-07 Affected versions changed · Red Hat
  4. 2026-10-15 Affected versions changed · CNA
  5. 2026-10-25 EPSS moved to the 50th–90th percentile

References

Patch 2

Advisory 1

Other 2

  • TI-2022-20281 Uncaught exception in engine.io CVSS 3.1HIGH 7.1
  • TI-2022-06052 Uncaught Exception in engine.io CVSS 3.1HIGH 7.5
  • TI-2026-42593 Socket.IO: Engine.IO WebTransport SID DoS CVSS 3.1HIGH 7.5
  • TI-2020-18427 Engine.IO before 4.0.0 allows attackers to cause a denial of service (resource… CVSS 3.1HIGH 7.5
  • TI-2023-14835 Uncaught exception in engine.io CVSS 3.1MEDIUM 6.5

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences