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Vulnerability record · CVE-2021-25735 · published 6 September 2021

CVE-2021-25735: Kubernetes vulnerability

Kubernetes · Kubernetes

A security issue was discovered in kube-apiserver that could allow node updates to bypass a Validating Admission Webhook. Clusters are only affected by this vulnerability if they run a Validating Admission Webhook for Nodes that denies admission based at least partially on the old state of the Node object. Validating Admission Webhook does not observe some previous fields.

6.5 CVSS 3.1 Medium EPSS 5.5% · top 7.5% CWE-372 · CWE-372
6.5CVSS 3.1 base score, v2 5.5
5.5%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

Description

A security issue was discovered in kube-apiserver that could allow node updates to bypass a Validating Admission Webhook. Clusters are only affected by this vulnerability if they run a Validating Admission Webhook for Nodes that denies admission based at least partially on the old state of the Node object. Validating Admission Webhook does not observe some previous fields.

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/kubernetes/kubernetes/issues/100096 PatchThird Party Advisory
https://groups.google.com/g/kubernetes-security-announce/c/FKAGqT4jx9Y Mailing ListThird Party Advisory
https://github.com/kubernetes/kubernetes/issues/100096 PatchThird Party Advisory
https://groups.google.com/g/kubernetes-security-announce/c/FKAGqT4jx9Y Mailing ListThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-25735), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.