How severe is CVE-2021-25735?

CVE-2021-25735 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.

Is CVE-2021-25735 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-25735?

CVE-2021-25735 affects Kubernetes. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-25735?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-25735 published?

CVE-2021-25735 was published on 2021-09-06 and last updated on 2026-06-17.

CVE-2021-25735

CVE-2021-25735 is a medium-severity vulnerability in Kubernetes with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-372.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 5.5
EPSS exploit prediction: 6% (92nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-372
Affected product: Kubernetes
Published: 2021-09-06
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-25735?: 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.
How severe is CVE-2021-25735?: CVE-2021-25735 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.
Is CVE-2021-25735 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-25735?: CVE-2021-25735 affects Kubernetes. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-25735?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-25735 published?: CVE-2021-25735 was published on 2021-09-06 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:kubernetes:kubernetes:*:*:*:*:*:*:*:*

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