CVE-2020-8559

Privilege Escalation in Kubernetes

The Kubernetes kube-apiserver in versions v1.6-v1.15, and versions prior to v1.16.13, v1.17.9 and v1.18.7 are vulnerable to an unvalidated redirect on proxied upgrade requests that could allow an attacker to escalate privileges from a node compromise to a full cluster compromise.

Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites. Typical impact: phishing and credential harvesting via a trusted domain.

CVE-2020-8559 has a CVSS score of 6.8 (Medium). The vector is network-reachable, high 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 (0.16.13, 0.17.9, 0.18.7, 1.16.13, 1.17.9, 1.18.7); upgrading removes the vulnerable code path.

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1. What is CVE-2020-8559? CVE-2020-8559 is a medium-severity open redirect vulnerability in k8s.io/apimachinery (go), affecting versions < 0.16.13. It is fixed in 0.16.13, 0.17.9, 0.18.7, 1.16.13, 1.17.9, 1.18.7. Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites.
2. How severe is CVE-2020-8559? CVE-2020-8559 has a CVSS score of 6.8 (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-2020-8559?
   • k8s.io/apimachinery (go) (versions < 0.16.13)
   • k8s.io/kubernetes (go) (versions < 1.16.13)
4. Is there a fix for CVE-2020-8559? Yes. CVE-2020-8559 is fixed in 0.16.13, 0.17.9, 0.18.7, 1.16.13, 1.17.9, 1.18.7. Upgrade to this version or later.
5. Is CVE-2020-8559 exploitable, and should I be worried? Whether CVE-2020-8559 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-2020-8559 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-2020-8559?
   • Upgrade k8s.io/apimachinery to 0.16.13 or later
   • Upgrade k8s.io/apimachinery to 0.17.9 or later
   • Upgrade k8s.io/apimachinery to 0.18.7 or later
   • Upgrade k8s.io/kubernetes to 1.16.13 or later
   • Upgrade k8s.io/kubernetes to 1.17.9 or later
   • Upgrade k8s.io/kubernetes to 1.18.7 or later

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