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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

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

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2020-15999?

O3 pinpoints whether CVE-2020-15999 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

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 50.6%, 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 July 13, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2021-11-03 — agencies required to remediate by 2021-11-17

.NET NuGet

CVE-2020-15999

CRITICAL

Heap buffer overflow in CefSharp

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

Published

Nov 3, 2020

Updated

Jul 13, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

7 known

EPSS Exploitation Probability

via FIRST.org ↗

50.6%probability of exploitation in next 30 days

High Risk99th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

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

Heap buffer overflow in Freetype in Google Chrome prior to 86.0.4240.111 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`CefSharp.Common`	all versions	85.3.130
.NETNuGet	`CefSharp.Wpf`	all versions	85.3.130
.NETNuGet	`CefSharp.WinForms`	all versions	85.3.130
.NETNuGet	`CefSharp.Wpf.HwndHost`	all versions	85.3.130

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.