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Fencer Intel
medium 5.9

CVE-2016-10536 json

Insecure Defaults Allow MITM Over TLS in engine.io-client

published 2018-05-31 8 y ago modified 2026-06-17 4 mo ago also GHSA-4r4m-hjwj-43p8 , EUVD-2019-0221

cvss
5.9
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.0%
EPSS 1.0% chance of exploitation in 30 days, percentile 62%
public exploits
0
none known

Summary

engine.io-client is the client for engine.io, the implementation of a transport-based cross-browser/cross-device bi-directional communication layer for Socket.IO. The vulnerability is related to the way that node.js handles the `rejectUnauthorized` setting. If the value is something that evaluates to false, certificate verification will be disabled. This is problematic as engine.io-client 1.6.8 and earlier passes in an object for settings that includes the rejectUnauthorized property, whether it has been set or not. If the value has not been explicitly changed, it will be passed in as `null`, resulting in certificate verification being turned off.

Patch / fix

  • npm engine.io-client 1.6.9

Exploit prediction

0.98% chance of exploitation in the next 30 days, higher than 62% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.0 5.9 CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:P/I:N/A:N
GitHub 3.0 5.9 CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
npm engine.io-client
<1.6.9
1.6.9

Affected products

  • HackerOne engine.io-client node module

Classification

Weakness
  • CWE-300 Channel Accessible by Non-Endpoint
  • CWE-295 Improper Certificate Validation

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.