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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.9 · CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2016-10536: 1.00% estimated exploitation activity in the next 30 days; percentile 62.78 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Affected versions of engine.io-client do not verify certificates by default, and as such may be vulnerable to Man-in-the-Middle attacks. The vulnerability is related to the way that node.js handles the rejectUnauthorized setting. If the value is something that evaluates to false, such as undefined or null, certificate verification will be disabled. Recommendation Update to version 1.6.9 or later. If you are unable to upgrade, ensure all calls to socket.io to have a rejectedUnauthorized: true flag.

Published by the source

18 Feb 2019, 23:39 UTC

Last modified by the source

8 Nov 2023, 03:58 UTC

Source last checked

26 Oct 2026, 12:25 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-4r4m-hjwj-43p8

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-4r4m-hjwj-43p8

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# Patch Next advisory brief: CVE-2016-10536

Advisory: Insecure Defaults Allow MITM Over TLS in engine.io-client
IDs: CVE-2016-10536, GHSA-4r4m-hjwj-43p8
Record: https://patchnext.com/advisories/cve-2016-10536 (revision 2, source checked 26 Oct 2026, 12:25 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: engine.io-client 1.6.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm engine.io-client: affected < 1.6.9; fixed in 1.6.9

## Suggested inspection (read-only)
- `npm ls engine.io-client --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on engine.io-client.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-4r4m-hjwj-43p8 (OSV record GHSA-4r4m-hjwj-43p8 lists affected ranges: npm engine.io-client >=0 <1.6.9 (fixed))
- Verified: https://github.com/advisories/GHSA-4r4m-hjwj-43p8 (GitHub-reviewed advisory GHSA-4r4m-hjwj-43p8 lists affected ranges: npm engine.io-client >=0 <1.6.9)

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