CVE-2020-8562

Bypass of Kubernetes API Server proxy TOCTOU

Severity Score

3.1

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

*SSVC

Descriptions

As mitigations to a report from 2019 and CVE-2020-8555, Kubernetes attempts to prevent proxied connections from accessing link-local or localhost networks when making user-driven connections to Services, Pods, Nodes, or StorageClass service providers. As part of this mitigation Kubernetes does a DNS name resolution check and validates that response IPs are not in the link-local (169.254.0.0/16) or localhost (127.0.0.0/8) range. Kubernetes then performs a second DNS resolution without validation for the actual connection. If a non-standard DNS server returns different non-cached responses, a user may be able to bypass the proxy IP restriction and access private networks on the control plane.

Como mitigación a un informe de 2019 y CVE-2020-8555, Kubernetes intenta impedir que las conexiones proxy accedan a las redes link-local o localhost cuando son realizadas conexiones impulsadas por el usuario a los servicios, pods, nodos o proveedores de servicios StorageClass. Como parte de esta mitigación, Kubernetes realiza una comprobación de resolución de nombres DNS y comprueba que las IPs de respuesta no estén en el rango link-local (169.254.0.0/16) o localhost (127.0.0/8). A continuación, Kubernetes lleva a cabo una segunda resolución de DNS sin comprobar para la conexión real. Si un servidor DNS no estándar devuelve diferentes respuestas no almacenadas en caché, un usuario puede ser capaz de omitir la restricción de la IP del proxy y acceder a redes privadas en el plano de control

*Credits: Javier Provecho

CVSS Scores

Attack Vector

Network

Attack Complexity

High

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Attack Vector

Network

Attack Complexity

High

Privileges Required

High

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Attack Vector

Network

Attack Complexity

Medium

Authentication

Single

Confidentiality

Partial

Integrity

None

Availability

None

* Common Vulnerability Scoring System

SSVC

Decision:-

Exploitation

Automatable

Tech. Impact

* Organization's Worst-case Scenario

Timeline

2020-02-03 CVE Reserved
2022-02-01 CVE Published
2023-12-19 EPSS Updated
2024-09-16 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition

CAPEC

References (3)

URL	Tag	Source
https://github.com/kubernetes/kubernetes/issues/101493	Issue Tracking
https://groups.google.com/g/kubernetes-security-announce/c/-MFX60_wdOY	Mailing List
https://security.netapp.com/advisory/ntap-20220225-0002	Third Party Advisory

URL	Date	SRC

URL	Date	SRC

URL	Date	SRC

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Kubernetes Search vendor "Kubernetes"		Kubernetes Search vendor "Kubernetes" for product "Kubernetes"				<= 1.18.18 Search vendor "Kubernetes" for product "Kubernetes" and version " <= 1.18.18"		-		Affected
Kubernetes Search vendor "Kubernetes"		Kubernetes Search vendor "Kubernetes" for product "Kubernetes"				>= 1.19.0 <= 1.19.10 Search vendor "Kubernetes" for product "Kubernetes" and version " >= 1.19.0 <= 1.19.10"		-		Affected
Kubernetes Search vendor "Kubernetes"		Kubernetes Search vendor "Kubernetes" for product "Kubernetes"				>= 1.20.0 <= 1.20.6 Search vendor "Kubernetes" for product "Kubernetes" and version " >= 1.20.0 <= 1.20.6"		-		Affected
Kubernetes Search vendor "Kubernetes"		Kubernetes Search vendor "Kubernetes" for product "Kubernetes"				1.21.0 Search vendor "Kubernetes" for product "Kubernetes" and version "1.21.0"		-		Affected