The Kubernetes kubelet component in versions 1.1-1.16.12, 1.17.0-1.17.8 and 1.18.0-1.18.5 do not account for disk usage by a pod which writes to its own /etc/hosts file. The /etc/hosts file mounted in a pod by kubelet is not included by the kubelet eviction manager when calculating ephemeral storage usage by a pod. If a pod writes a large amount of data to the /etc/hosts file, it could fill the storage space of the node and cause the node to fail.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-8557
• kubernetes/kubernetes#93032
• kubernetes/kubernetes#92921
• kubernetes/kubernetes@530f199
• kubernetes/kubernetes@68750fe
• kubernetes/kubernetes@7fd849c
• https://groups.google.com/g/kubernetes-security-announce/c/cB_JUsYEKyY/m/vVSO61AhBwAJ
• https://security.netapp.com/advisory/ntap-20200821-0002