Bypass of Kubernetes API Server proxy TOCTOU
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
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.
Timeline
- CVE published
- Record last updated
Affected versions
- Kubernetes Kubernetes
All versions
- k8s.io/kubernetesGo
From 1.21.0 · through 1.21.1
- k8s.io/kubernetesGo
From 1.20.0 · through 1.20.7
- k8s.io/kubernetesGo
From 1.19.0 · through 1.19.11
- k8s.io/kubernetesGo
through 1.18.19