#VU56245 Input validation error in Kubernetes - CVE-2021-25735

Vulnerability identifier: #VU56245

Vulnerability risk: Medium

CVSSv4.0: 2.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/U:Green]

CVE-ID: CVE-2021-25735

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
Kubernetes
Server applications / Frameworks for developing and running applications

Vendor: Kubernetes

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient validation of user-supplied input in kube-apiserver that could allow Node updates to bypass a Validating Admission Webhook. An authenticated user could exploit this by modifying Node properties to values that should have been prevented by registered admission webhooks.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Kubernetes: 1.18.0 - 1.19.9, 1.20.0 - 1.20.5

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External links
https://github.com/kubernetes/kubernetes/issues/100096
https://bugzilla.redhat.com/show_bug.cgi?id=1937562

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.