Bypass of Kubernetes API Server proxy TOCTOU
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- High
- Impact type
- —
- Confidentiality · integrity · availability
- Low · None · None
- Fix status
- Deferred Red Hat: fix deferred
Attack profile from CVSS 3.1 · NVD. Fix status from CNA, GitHub and Red Hat.
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.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Kubernetes | Kubernetes | all versions | — | No fix listed | CNA |
| — | k8s.io/kubernetes (Go) | 1.21.0 – 1.21.1 | — | No fix listed | GHSA-qh36-44jv-c8xj |
| — | k8s.io/kubernetes (Go) | 1.20.0 – 1.20.7 | — | No fix listed | GHSA-qh36-44jv-c8xj |
| — | k8s.io/kubernetes (Go) | 1.19.0 – 1.19.11 | — | No fix listed | GHSA-qh36-44jv-c8xj |
| — | k8s.io/kubernetes (Go) | up to 1.18.19 | — | No fix listed | GHSA-qh36-44jv-c8xj |
- Kubernetes VendorKubernetes Affected all versions Fixed in — No fix listed CNA
- k8s.io/kubernetes (Go) Vendor— Affected 1.21.0 – 1.21.1 Fixed in — No fix listed GHSA-qh36-44jv-c8xj
- k8s.io/kubernetes (Go) Vendor— Affected 1.20.0 – 1.20.7 Fixed in — No fix listed GHSA-qh36-44jv-c8xj
- k8s.io/kubernetes (Go) Vendor— Affected 1.19.0 – 1.19.11 Fixed in — No fix listed GHSA-qh36-44jv-c8xj
- k8s.io/kubernetes (Go) Vendor— Affected up to 1.18.19 Fixed in — No fix listed GHSA-qh36-44jv-c8xj
CPE configurations NVD · 2
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:kubernetes:kubernetes:*:*:*:*:*:*:*:* | up to 1.18.18; 1.19.0 – 1.19.10; 1.20.0 – 1.20.6 | Vulnerable | Kubernetes |
| cpe:2.3:a:kubernetes:kubernetes:1.21.0:*:*:*:*:*:*:* | 1.21.0 | Vulnerable | Kubernetes |
- cpe:2.3:a:kubernetes:kubernetes:*:*:*:*:*:*:*:* Versions up to 1.18.18; 1.19.0 – 1.19.10; 1.20.0 – 1.20.6 Vulnerable ·Kubernetes
- cpe:2.3:a:kubernetes:kubernetes:1.21.0:*:*:*:*:*:*:* Versions 1.21.0 Vulnerable ·Kubernetes
Remediation
No fixed version listed by the sources yet.
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat OpenShift Container Platform 3.11 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2020-8562
- 2026-10-03 Alias added: GHSA-qh36-44jv-c8xj
References
Advisory 4
Other 5
- https://kubernetes.io/blog/2026/05/26/reconciling-unfixed-kubernetes-cves/
- https://github.com/kubernetes/kubernetes/issues/101493#issuecomment-2272095629
- https://github.com/kubernetes/kubernetes
- https://kubernetes.io/blog/2026/05/26/reconciling-unfixed-kubernetes-cves
- https://security.netapp.com/advisory/ntap-20220225-0002
More Kubernetes vulnerabilities
- TI-2018-16130 Improper privilege management in Kubernetes CVSS 3.0CRITICAL 9.8
- TI-2019-08418 Kubernetes kubelet exposes /debug/pprof info on healthz port CVSS 3.1HIGH 8.2
- TI-2023-05086 Kubernetes - Windows nodes - Insufficient input sanitization in in-tree storage plugin leads to privilege escalation CVSS 3.1HIGH 8.8
- TI-2023-03433 Kubernetes - Windows nodes - Insufficient input sanitization leads to privilege escalation CVSS 3.1HIGH 8.8
- TI-2023-02285 Bypass of seccomp profile enforcement CVSS 3.1MEDIUM 5.5
- TI-2017-14755 Link following in Kubernetes CVSS 3.0CRITICAL 9.6
Sources
- CVE-2020-8562 · CVE Program
- CVE-2020-8562 · NVD
- FIRST EPSS
- GHSA-qh36-44jv-c8xj · GitHub Advisory Database · CC BY 4.0
- CVE-2020-8562 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences