How severe is CVE-2020-20136?

CVE-2020-20136 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-20136 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (72nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-20136?

CVE-2020-20136 affects Quantconnect Lean. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-20136?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2020-20136 published?

CVE-2020-20136 was published on 2020-12-14 and last updated on 2026-06-17.

CVE-2020-20136

CVE-2020-20136 is a critical-severity vulnerability in Quantconnect Lean with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-502.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (72nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-502
Affected product: Quantconnect Lean
Published: 2020-12-14
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2020-20136?: 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.
How severe is CVE-2020-20136?: CVE-2020-20136 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-20136 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (72nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-20136?: CVE-2020-20136 affects Quantconnect Lean. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-20136?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2020-20136 published?: CVE-2020-20136 was published on 2020-12-14 and last updated on 2026-06-17.

References

https://github.com/QuantConnect/Lean/issues/3537

Affected products (1)

cpe:2.3:a:quantconnect:lean:*:*:*:*:*:*:*:*

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