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.NET
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CRITICAL severity

CVE-2020-20136 — QuantConnect.Common

CRITICAL

CVE-2020-20136 is a critical-severity (CVSS 9.8) Deserialization of Untrusted Data vulnerability in QuantConnect.Common. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

QuantConnect Lean vulnerable to insecure deserialization

Also known asGHSA-ww7r-278h-48mh
Published
Updated
Affected
1 pkg
Patched
See advisory
Exploits
1 known
Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs75th percentile — riskier than 75% of all scored CVEsHighest risk
0.00%0.68%1.36%2.04%0.3%1.5%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
.NETQuantConnect.Common

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
.NETNuGetQuantConnect.Common≥ 2.3.0.0No fix

Affected Products

1 product · 1 configurations
Application
leanquantconnect
≥ 2.3.0.0 && ≤ 2.4.0.1
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

QuantConnect Lean versions from 2.3.0.0 to 2.4.0.1 are affected by an in…

github.comNVDDec 2020

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for QuantConnect.Common, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    The records we use list no patched version of QuantConnect.Common for CVE-2020-20136. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

  3. Mitigate without a patch

    Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Frequently Asked Questions

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.
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CVE-2020-20136: QuantConnect Deserialization (Critical 9.8)