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Fencer Intel
medium 4.1

CVE-2020-8561 json

Webhook redirect in kube-apiserver

published 5y ago modified last mo. also GHSA-74j8-88mm-7496 , EUVD-2021-2002

cvss
4.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.1%
EPSS 2.1% chance of exploitation in 30 days, percentile 81%
public exploits
0
none known

Summary

A security issue was discovered in Kubernetes where actors that control the responses of MutatingWebhookConfiguration or ValidatingWebhookConfiguration requests are able to redirect kube-apiserver requests to private networks of the apiserver. If that user can view kube-apiserver logs when the log level is set to 10, they can view the redirected responses and headers in the logs.

Patch / fix

  • kubernetes Debian 14, Debian 13, Debian 12 1.20.5+really1.20.2-1

debian advisories DEBIAN-CVE-2020-8561

  • kubernetes1.33 openSUSE Tumbleweed 1.33.13-2.1
  • kubernetes1.34 openSUSE Tumbleweed 1.34.10-1.1
  • kubernetes1.35 openSUSE Tumbleweed 1.35.7-1.1
  • kubernetes1.36 openSUSE Tumbleweed 1.36.3-1.1

opensuse advisories openSUSE-SU-2026:11388-1openSUSE-SU-2026:11389-1openSUSE-SU-2026:11390-1openSUSE-SU-2026:11391-1

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-8561 updated cvss 4.1

kubernetes: Webhook redirect in kube-apiserver

  • Red Hat OpenShift Container Platform 3.11 atomic-openshift, atomic-openshift-pod, atomic-openshift-node, atomic-openshift-tests, atomic-openshift-master, atomic-openshift-clients, +7 more
    affected: no fix planned “Out of support scope”
  • Red Hat OpenShift Container Platform 4 openshift, openshift-clients, openshift-kubelet, openshift-hyperkube, openshift-kube-apiserver, openshift-kube-scheduler, +2 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.10% chance of exploitation in the next 30 days, higher than 81% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 4.1 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:N/A:N
NVD 3.1 4.1 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:N/A:N
NVD 2.0 4.0 AV:N/AC:L/Au:S/C:P/I:N/A:N
GitHub 3.1 4.1 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
go k8s.io/kubernetes
<=1.22.2
 no fix listed

Affected products

  • Kubernetes Kubernetes

Classification

Weakness
  • CWE-441 Unintended Proxy or Intermediary
  • CWE-610 Externally Controlled Reference to a Resource in Another Sphere
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.