A security issue was discovered in kube-apiserver that could allow node updates to bypass a Validating Admission Webhook. You are only affected by this vulnerability if you run a Validating Admission Webhook for Nodes that denies admission based at least partially on the old state of the Node object.
This issue has been rated Medium (CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H), and assigned CVE-2021-25735.
Note: This only impacts validating admission plugins that rely on old values in certain fields, and does not impact calls from kubelets that go through the built-in NodeRestriction admission plugin.
Affected Versions- kube-apiserver v1.20.0 - v1.20.5
-
kube-apiserver v1.19.0 - v1.19.9
-
kube-apiserver <= v1.18.17
Fixed Versions
This issue is fixed in the following versions:
-
kube-apiserver v1.21.0
-
kube-apiserver v1.20.6
-
kube-apiserver v1.19.10
-
kube-apiserver v1.18.18
Detection
If you find evidence that this vulnerability has been exploited, please contact security@kubernetes.io
Additional Details
See Kubernetes Issue #100096 for more details.
Acknowledgements
This vulnerability was reported by Rogerio Bastos & Ari Lima from RedHat
Thank You,
Tim Allclair on behalf of the Kubernetes Product Security Committee