How severe is CVE-2020-16017?

CVE-2020-16017 has a CVSS score of 9.6/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-16017?

CVE-2020-16017 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-2020-16017?

Update CefSharp.Common to 86.0.241 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-16017 is resolved across your whole dependency graph.

How do I detect CVE-2020-16017 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-2020-16017 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-2020-16017 actively exploited in the wild?

Yes. There are 3 known exploit references for CVE-2020-16017, including 3 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-2020-16017?

CVE-2020-16017 has an EPSS (Exploit Prediction Scoring System) score of 2.7%, placing it in the 86th 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 indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

Is CVE-2020-16017 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2020-16017 (Google Chrome Use-After-Free 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-2020-16017?

CVE-2020-16017 is classified as Use After Free (CWE-416). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-16017 published, and has it been updated?

CVE-2020-16017 was published on January 8, 2021 and was last updated on March 14, 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

CRITICAL severity

CVE-2020-16017 — CefSharp.Common

CRITICAL

CVE-2020-16017 is a critical-severity (CVSS 9.6) Use After Free 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.

Use after free in CefSharp

Also known asGHSA-gvqv-779r-4jgp

Published

Jan 8, 2021

Updated

Mar 14, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

3 known

Exploitation data as of Oct 23, 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-2020-16017.

EPSS Exploitation Probability

via FIRST.org ↗

2.7%probability of exploitation in next 30 days

Lower Risk-0.02%

Lower risk than most CVEs86th percentile — riskier than 86% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2020-16017 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% 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-2020-16017: Use after free in site isolation

Google is aware of reports that exploits for CVE-2020-16013 and CVE-2020-16017 exist in the wild.

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

1 product · 1 configurations

Application

chromegoogle

< 86.0.4240.198

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.

Use after free in site isolation in Google Chrome prior to 86.0.4240.198…

chromereleases.googleblog.comChromeNov 2020

Use after free in site isolation in Google Chrome prior to 86.0.4240.198…

chromereleases.googleblog.comGoogle-sheetNov 2020

Use after free in site isolation in Google Chrome prior to 86.0.4240.198…

cisa.govCISAJul 2021

Detection & mitigation playbook

Open-source dependency

Detect
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.
Fix
Update CefSharp.Common to 86.0.241 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-16017 is resolved across your whole dependency graph.
Workarounds
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.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Product	Fixed in	Advisory
Red Hat Enterprise Linux 6 Supplementary	`chromium-browser-0:86.0.4240.198-1.el6_10`	RHSA-2020:5165

Frequently Asked Questions

CVE-2020-16017: Use after free in site isolation - https://chromereleases.googleblog.com/2020/11/stable-channel-update-for-desktop_11.html - https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-16017 Google is aware of reports that exploits for CVE-2020-16013 and CVE-2020-16017 exist in the wild. There is currently little to no public information on the issue other than it has been flagged as `High` severity.

O3 Security · Impact-Aware SCA

Is CVE-2020-16017 in your dependencies?

Find it across NuGet, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

9.6/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

CWE Classification

CWE-416Use After Free

Weaponization

No known public exploit tooling found.

OpenSSF Scorecard

Package health score

CefSharp

5.0/10

Code-Review2/10

Maintained10/10

Branch-ProtectionN/A

Assessed Oct 19, 2026

Timeline

First exploit

Nov 11, 2020

Disclosed

Jan 8, 2021

KEV added

Nov 3, 2021

Last updated

Mar 14, 2026

Identifiers

CVE-2020-16017

GHSA-gvqv-779r-4jgp

References

Advisorychromereleases.googleblog.com Advisorynvd.nist.gov Reportcrbug.com Webcisa.gov Webgithub.com

Related vulnerabilities

Also affects CefSharp.Common

This CVE is critical severity; 1 of 7 other CVEs affecting CefSharp.Common is rated as high or higher (top: critical).

CVE-2026-48796GHSA-4c29-gfrp-g6x9GHSA-j646-gj5p-p45gCVE-2022-0609CVE-2020-16009CVE-2020-16013CVE-2020-15999

Also affects CefSharp.Wpf

This CVE is critical severity — higher than any of the other 1 CVE affecting CefSharp.Wpf (highest there: high).

GHSA-f87w-3j5w-v58p

Provenance

Sources

OSV.devNVDCISA KEVFIRST.org (EPSS)

Last verifiedMar 14, 2026

CVE-2020-16017 — CefSharp.Common

Exploitation Status

Actively exploited in the wild

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Fixing This On Your OS

Frequently Asked Questions

Is CVE-2020-16017 in your dependencies?