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[kubernetes] CVE-2021-25735: Validating Admission Webhook does not observe some previous fields
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From: Tim Allclair <timallclair () gmail com>
Date: Wed, 14 Apr 2021 09:06:02 -0700
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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
<https://www.first.org/cvss/calculator/3.0#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
<https://github.com/kubernetes/kubernetes/issues/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
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[kubernetes] CVE-2021-25735: Validating Admission Webhook does not observe some previous fields Tim Allclair (Apr 14)
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