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Kubernetes: CVE-2020-8562: Bypass of Kubernetes API Server proxy TOCTOU

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Kubernetes: CVE-2020-8562: Bypass of Kubernetes API Server proxy TOCTOU

Severity
4
CVSS
(AV:N/AC:M/Au:S/C:P/I:N/A:N)
Published
02/01/2022
Created
03/11/2022
Added
03/10/2022
Modified
03/28/2022

Description

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.

Solution(s)

  • kubernetes-upgrade-1_18_19
  • kubernetes-upgrade-1_19_11
  • kubernetes-upgrade-1_20_7
  • kubernetes-upgrade-1_21_0

References

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