CVE-2021-25735

Name: CVE-2021-25735
Creator: NVD / NIST
Published: 2021-09-06T12:15:07.617+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 5.23%

Last modified Jun 17, 2026

CVE-2021-25735 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. 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. EPSS estimates a 5.23% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

5.23%

91.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-372

Affected Software

Vendor	Product	Versions
Kubernetes	Kubernetes	< 1.18.18
Kubernetes	Kubernetes	>= 1.19.0, < 1.19.10
Kubernetes	Kubernetes	>= 1.20.0, < 1.20.6

References

https://github.com/kubernetes/kubernetes/issues/100096Patch, Third Party Advisory
https://groups.google.com/g/kubernetes-security-announce/c/FKAGqT4jx9YMailing List, Third Party Advisory
https://github.com/kubernetes/kubernetes/issues/100096Patch, Third Party Advisory
https://groups.google.com/g/kubernetes-security-announce/c/FKAGqT4jx9YMailing List, Third Party Advisory

Timeline

Published: Sep 6, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-25735?

How severe is CVE-2021-25735?

CVE-2021-25735 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 5.23% probability of exploitation in the next 30 days.

How do I fix CVE-2021-25735?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-25735?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST