CVE-2020-8562 is a vulnerability in Kubernetes
Published on February 1, 2022
Bypass of Kubernetes API Server proxy TOCTOU
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.
Vulnerability Analysis
CVE-2020-8562 is exploitable with network access, and requires user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a small impact on integrity and availability.
Weakness Type
What is a TOCTTOU Vulnerability?
The software checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the software to perform invalid actions when the resource is in an unexpected state. This weakness can be security-relevant when an attacker can influence the state of the resource between check and use. This can happen with shared resources such as files, memory, or even variables in multithreaded programs.
CVE-2020-8562 has been classified to as a TOCTTOU vulnerability or weakness.
Products Associated with CVE-2020-8562
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Affected Versions
Kubernetes:- Version unspecified, <= v1.18.18 is affected.
- Version next of v1.18.18 and below unspecified is unknown.
- Version unspecified, <= v1.19.10 is affected.
- Version next of v1.19.10 and below unspecified is unknown.
- Version unspecified, <= v1.20.6 is affected.
- Version next of v1.20.6 and below unspecified is unknown.
- Version unspecified, <= v1.21.0 is affected.
- Version next of v1.21.0 and below unspecified is unknown.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.