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TI-2026-73305 Aliases CVE-2026-102599

Uncaught exception in Engine.IO lets clients crash Node.js processes

Priority MEDIUM 40CWE-248Published · 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 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-248.

Summary

Engine.IO from 6.6.0 before 6.6.10 is affected, and Socket.IO from 6.6.0 before 6.6.10 is affected as well. A transport upgrade derives the protocol revision from the upgrade request instead of the revision stored on the session, which leads to an uncaught exception (CWE-248). A remote client that establishes a valid session can send a crafted heartbeat packet that terminates the Node.js process, causing a denial of service.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

Socket.IO enables bidirectional and low-latency communication for every platform. From Engine.IO 6.6.0 until 6.6.10, a transport upgrade can independently derive an Engine.IO protocol revision from the upgrade request instead of enforcing the revision stored on the existing session. A malicious client can establish a valid session and send an upgrade request with a different or omitted EIO query parameter, attaching a transport with incompatible parser and heartbeat behavior. A crafted heartbeat packet can then trigger an uncaught exception and terminate the Node.js process, including when Engine.IO v3 compatibility is disabled because an omitted EIO value is interpreted as revision 3 on the affected path. This issue is fixed in Engine.IO 6.6.10.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00576 47th percentileScored 2026-11-07
Fix Partial socket.io (socketio): 6.6.10engine.io (npm): 6.6.10Red Hat: 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
socketiosocket.io6.6.0 to before 6.6.106.6.10Patch availableCNA
—engine.io (npm)6.6.0 to before 6.6.106.6.10Patch availableGHSA-2gc4-cqfq-p2gv
  • socket.io Vendorsocketio Affected 6.6.0 to before 6.6.10 Fixed in 6.6.10 Patch available CNA
  • engine.io (npm) Vendor— Affected 6.6.0 to before 6.6.10 Fixed in 6.6.10 Patch available GHSA-2gc4-cqfq-p2gv

Remediation

Update engine.io to 6.6.10. The sources list no fixed version for socket.io. Red Hat lists Red Hat Enterprise Linux AI (RHEL AI) 3 as affected, with no plan available.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

  • Fix · CNA socket.io (socketio) Fixed in 6.6.10
  • Fix · GHSA-2gc4-cqfq-p2gv engine.io (npm) Fixed in 6.6.10 Advisory →

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
Not affected: 3 products
  • Red Hat Enterprise Linux 10
  • Red Hat Fuse 7
  • Red Hat Hardened Images

Timeline

  1. 2026-10-13 Threatist record created from CVE-2026-102599
  2. 2026-10-14 Priority changed: MEDIUM → LOW
  3. 2026-10-15 Affected versions changed · Red Hat
  4. 2026-10-15 CVSS score added · Red Hat
  5. 2026-10-18 CISA SSVC decision points changed
  6. 2026-10-18 Priority changed: LOW → MEDIUM
  7. 2026-10-19 Affected versions changed · Red Hat
  8. 2026-10-20 Affected versions changed · Red Hat

References

Other 4

  • TI-2022-20281 Uncaught exception in engine.io CVSS 3.1HIGH 7.1
  • TI-2022-02236 Socket.io - Improper type validation in attachment parsing CVSS 3.1CRITICAL 10.0
  • TI-2026-25581 socket.io allows an unbounded number of binary attachments CVSS 4.0HIGH 8.7
  • TI-2022-06052 Uncaught Exception in engine.io CVSS 3.1HIGH 7.5
  • TI-2023-15971 Insufficient validation when decoding a Socket.IO packet CVSS 3.1HIGH 7.5
  • TI-2026-48537 Socket.IO: Zero-attachment Memory Exhaustion CVSS 3.1HIGH 7.5
See all 18 →

Sources

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