How severe is CVE-2020-16009?

CVE-2020-16009 has a CVSS score of 8.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-16009?

CVE-2020-16009 affects the following packages: CefSharp.Common (NuGet), CefSharp.Wpf (NuGet), CefSharp.WinForms (NuGet), CefSharp.Wpf.HwndHost (NuGet). Ecosystems affected: NuGet.

How do I fix CVE-2020-16009?

Update CefSharp.Common to 86.0.241 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-16009 is resolved across your whole dependency graph.

How do I detect CVE-2020-16009 in my NuGet dependencies?

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

How do I mitigate CVE-2020-16009 if there is no patch (or I can't update yet)?

Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Is CVE-2020-16009 actively exploited in the wild?

Yes. There are 5 known exploit references for CVE-2020-16009, including 5 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2020-16009?

CVE-2020-16009 has an EPSS (Exploit Prediction Scoring System) score of 48.3%, placing it in the 99th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score warrants monitoring and prompt remediation.

Is CVE-2020-16009 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2020-16009 (Google Chromium V8 Type Confusion Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03. CISA required all US federal civilian agencies to remediate this vulnerability by 2022-05-03. The required action was: Apply updates per vendor instructions. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2020-16009?

CVE-2020-16009 is classified as Out-of-bounds Write (CWE-787), CWE-843 (CWE-843). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-16009 published, and has it been updated?

CVE-2020-16009 was published on November 3, 2020 and was last updated on October 24, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

.NET

.NET NuGet

CISA KEV · ACTIVELY EXPLOITED

HIGH severity

CVE-2020-16009 — CefSharp.Common

HIGH

CVE-2020-16009 is a high-severity (CVSS 8.8) Out-of-bounds Write vulnerability in CefSharp.Common. It is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) — treat it as actively exploited and patch now. A fix is available for CefSharp.Common — see the affected versions and patch details below.

Inappropriate implementation in V8

Also known asGHSA-m7mf-48hp-5qmr

Published

Nov 3, 2020

Updated

Oct 24, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

5 known

Exploitation data as of Oct 24, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2021-11-03. Federal agencies were required to remediate by 2022-05-03.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2020-16009.

EPSS Exploitation Probability

via FIRST.org ↗

48.3%probability of exploitation in next 30 days

High Risk0.00%

Lower risk than most CVEs99th percentile — riskier than 99% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2020-16009 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

4 pkgs affected

.NETCefSharp.Common.NETCefSharp.Wpf.NETCefSharp.WinForms.NETCefSharp.Wpf.HwndHost

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

CVE-2020-16009: Inappropriate implementation in V8

Google is aware of reports that exploits for CVE-2020-16009 exist in the wild.

Allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.

There is currently little to no public information on the issue other than it has been flagged as High severity.

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`CefSharp.Common`	all versions	86.0.241`dotnet add package CefSharp.Common --version 86.0.241`
.NETNuGet	`CefSharp.Wpf`	all versions	86.0.241`dotnet add package CefSharp.Wpf --version 86.0.241`
.NETNuGet	`CefSharp.WinForms`	all versions	86.0.241`dotnet add package CefSharp.WinForms --version 86.0.241`
.NETNuGet	`CefSharp.Wpf.HwndHost`	all versions	86.0.241`dotnet add package CefSharp.Wpf.HwndHost --version 86.0.241`

Affected Products

8 products · 11 configurations

Application

cefsharpcefsharp

< 86.0.241

range

debian linuxdebian

1 version

10.0

fedorafedoraproject

2 versions

3233

Application

chromegoogle

< 86.0.4240.183

range

Application

edgemicrosoft

< 86.0.622.63

range

Application

edge chromiummicrosoft

< 86.0.4240.183

range

Exploits & PoCs

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