CVE-2020-15999

Heap buffer overflow in CefSharp

References

• https://www.secpod.com/blog/chrome-zero-day-under-active-exploitation-patch-now/
• https://www.zdnet.com/article/google-releases-chrome-security-update-to-patch-actively-exploited-zero-day/
• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-15999
• https://magpcss.org/ceforum/viewtopic.php?f=10&t=17942

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

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.

A write operation targets a memory location beyond the intended buffer boundary. Typical impact: memory corruption, crash, or arbitrary code execution.

CVE-2020-15999 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (85.3.130); upgrading removes the vulnerable code path.

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Upgrade to 85.3.130 or higher

1. What is CVE-2020-15999? CVE-2020-15999 is a medium-severity out-of-bounds write vulnerability in CefSharp.Common (nuget), affecting versions < 85.3.130. It is fixed in 85.3.130. A write operation targets a memory location beyond the intended buffer boundary.
2. How severe is CVE-2020-15999? CVE-2020-15999 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2020-15999?
   • CefSharp.Common (nuget) (versions < 85.3.130)
   • CefSharp.Wpf (nuget) (versions < 85.3.130)
   • CefSharp.WinForms (nuget) (versions < 85.3.130)
   • CefSharp.Wpf.HwndHost (nuget) (versions < 85.3.130)
4. Is there a fix for CVE-2020-15999? Yes. CVE-2020-15999 is fixed in 85.3.130. Upgrade to this version or later.
5. Is CVE-2020-15999 exploitable, and should I be worried? Whether CVE-2020-15999 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2020-15999 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2020-15999?
   • Upgrade CefSharp.Common to 85.3.130 or later
   • Upgrade CefSharp.Wpf to 85.3.130 or later
   • Upgrade CefSharp.WinForms to 85.3.130 or later
   • Upgrade CefSharp.Wpf.HwndHost to 85.3.130 or later

Other vulnerabilities in CefSharp.Common