How severe is CVE-2020-15999?

CVE-2020-15999 has a CVSS score of 9.6/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-15999?

CVE-2020-15999 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-2020-15999?

Update CefSharp.Common to 85.3.130 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-15999 is resolved across your whole dependency graph.

How do I detect CVE-2020-15999 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-2020-15999 if there is no patch (or I can't update yet)?

Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Is CVE-2020-15999 actively exploited in the wild?

Yes. There are 7 known exploit references for CVE-2020-15999, including 6 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-2020-15999?

CVE-2020-15999 has an EPSS (Exploit Prediction Scoring System) score of 63.9%, 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. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2020-15999 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2020-15999 (Google Chrome FreeType Heap Buffer Overflow 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 2021-11-17. 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-2020-15999?

CVE-2020-15999 is classified as Out-of-bounds Write (CWE-787), CWE-120 (CWE-120). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-15999 published, and has it been updated?

CVE-2020-15999 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

CRITICAL severity

CVE-2020-15999 — CefSharp.Common

CRITICAL

CVE-2020-15999 is a critical-severity (CVSS 9.6) 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.

Heap buffer overflow in CefSharp

Also known asA-171232105ASB-A-171232105GHSA-pv36-h7jh-qm62

Published

Nov 3, 2020

Updated

Oct 24, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

7 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 2021-11-17.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2020-15999.

EPSS Exploitation Probability

via FIRST.org ↗

63.9%probability of exploitation in next 30 days

High Risk+19.59%

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-2020-15999 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the 50–90% 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

Impact

A memory corruption bug(Heap overflow) in the FreeType font rendering library.

This can be exploited by attackers to execute arbitrary code by using specially crafted fonts with embedded PNG images .

As per https://www.secpod.com/blog/chrome-zero-day-under-active-exploitation-patch-now/

Google is aware of reports that an exploit for CVE-2020-15999 exists in the wild.

Patches

Upgrade to 85.3.130 or higher

References

To review the CEF/Chromium patch see https://bitbucket.org/chromiumembedded/cef/commits/cd6cbe008b127990036945fb75e7c2c1594ab10d

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`CefSharp.Common`	all versions	85.3.130`dotnet add package CefSharp.Common --version 85.3.130`
.NETNuGet	`CefSharp.Wpf`	all versions	85.3.130`dotnet add package CefSharp.Wpf --version 85.3.130`
.NETNuGet	`CefSharp.WinForms`	all versions	85.3.130`dotnet add package CefSharp.WinForms --version 85.3.130`
.NETNuGet	`CefSharp.Wpf.HwndHost`	all versions	85.3.130`dotnet add package CefSharp.Wpf.HwndHost --version 85.3.130`

Affected Products

6 products · 6 configurations

debian linuxdebian

1 version

10.0

fedorafedoraproject

1 version

Application

freetypefreetype

≥ 2.6.0 && < 2.10.4

range

Application

chromegoogle

< 86.0.4240.111

range

Application

ontap select deploy administration utilitynetapp

all

Application

backports sleopensuse

1 version

15.0

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.