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Critical, CVSS 9.8

QuantConnect Lean vulnerable to insecure deserialization

CVE-2020-20136GHSA-ww7r-278h-48mh

What to do

Vendor response not established. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • NuGet quantconnect.common

    Affected
    >= 2.3.0.0, <= 2.4.0.1
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
9.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
  • CVE-2020-20136: 1.54% estimated exploitation activity in the next 30 days; percentile 74.90 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

QuantConnect Lean versions from 2.3.0.0 to 2.4.0.1 are affected by an insecure deserialization vulnerability due to insecure configuration of TypeNameHandling property in Json.NET library. One may avoid this issue by only running Lean in an environment where data provided is trusted.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-ww7r-278h-48mh

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2020-20136

Advisory: QuantConnect Lean vulnerable to insecure deserialization
IDs: CVE-2020-20136, GHSA-ww7r-278h-48mh
Record: https://patchnext.com/advisories/cve-2020-20136 (revision 1, source checked 26 Oct 2026, 16:59 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet quantconnect.common: affected >= 2.3.0.0, <= 2.4.0.1

## Suggested inspection (read-only)
- NuGet quantconnect.common: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on quantconnect.common.
- 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://github.com/advisories/GHSA-ww7r-278h-48mh (GitHub-reviewed advisory GHSA-ww7r-278h-48mh lists affected ranges: NuGet quantconnect.common >=2.3.0.0 <=2.4.0.1)

Commands are suggestions: review each one before running it.

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