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Fencer Intel
high 7.5

CVE-2026-102599 json

Socket.IO: Engine.IO Protocol Revision Mismatch DoS

published last mo. modified 24d ago also EUVD-2026-100462 , GHSA-2gc4-cqfq-p2gv

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 47%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm engine.io 6.6.10
  • socket socket.io 6.6.10

Is CVE-2026-102599 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2026-102599 updated cvss 7.5

engine.io: engine.io: Denial of Service via protocol revision mismatch during transport upgrade

  • 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: workaround, no fix available
  • Red Hat Enterprise Linux 10 grafana Red Hat Fuse 7 engine.io
    not affected: vulnerable code not present
  • Red Hat Hardened Images grafana12.4, grafana13.1, grafana13.2
    not affected: component 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
24d ago

Exploit prediction

0.58% chance of exploitation in the next 30 days, higher than 47% of all scored CVEs (FIRST EPSS, 2026-11-09).

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
>=6.6.0, <6.6.10
6.6.10

Affected products

  • socketio socket.io

Classification

Weakness

References

Sources

Fencer Intel 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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.