CVE-2021-25735

medium

Published 2021-05-28 · Modified 2026-02-04

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CVSS v3

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

CVSS v4 NEW

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not yet in upstream

VIR risk

5.5

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.

Predictions

Exploit likelihood

30%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here with source_tier=community-verified.

OS impact

SUSE Affected 1 release

Version	Status	Fixed in
—	Affected	—

Arch Fixed 1 release

Version	Status	Fixed in
—	Fixed	`1.21.0-1`

Debian Fixed 5 releases

Version	Status	Fixed in
trixie	Fixed	`1.20.5+really1.20.2-1`
sid	Fixed	`1.20.5+really1.20.2-1`
forky	Fixed	`1.20.5+really1.20.2-1`
bullseye	Fixed	`1.20.5+really1.20.2-1`
bookworm	Fixed	`1.20.5+really1.20.2-1`

Package impact

Ecosystem	Package	Vulnerable	Fixed
Go	k8s.io/kubernetes	`>=1.20.0,<1.20.6`	`1.20.6`
Go	k8s.io/kubernetes	`>=1.19.0,<1.19.10`	`1.19.10`
Go	k8s.io/kubernetes	`<1.18.18`	`1.18.18`

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.