CVE-2021-25735
CWE-372Published: September 6, 2021· Updated: Jun 17, 2026
Official 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.
Technical Analysis
CVE-2021-25735 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation requires high privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
A successful exploit results in full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 6.5.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
All References (4)
Quick Facts
Related CVEs (CWE-372)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-25735 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts