Validating Admission Webhook does not observe some previous fields
CVE-2021-25735

6.5MEDIUM

Key Information:

Vendor

Kubernetes
Status
Kubernetes
Vendor
CVE Published:
6 September 2021

Badges

👾 Exploit Exists🟡 Public PoC🟣 EPSS 14%

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.

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Deploy the Patch

Affected Version(s)

Kubernetes <= 1.18.17

Kubernetes <= 1.19.9

Kubernetes <= 1.20.5

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2021-25735
Created by darryk10

References

https://groups.google.com/g/kubernetes-security-announce/...
x_refsource_MISC
https://github.com/kubernetes/kubernetes/issues/100096
x_refsource_MISC

EPSS Score

14% chance of being exploited in the next 30 days.

CVSS V3.1

Score:
6.5
Severity:
MEDIUM
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
High
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability Reserved

Credit

Rogerio Bastos & Ari Lima
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