Bypass of Kubernetes API Server proxy TOCTOU
Summary
| CVE | CVE-2020-8562 |
|---|---|
| State | PUBLISHED |
| Assigner | kubernetes |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2022-02-01 11:15:10 UTC |
| Updated | 2026-06-01 23:16:14 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 3.1 LOW from [email protected]
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
EPSS: 0.000560000 probability, percentile 0.177470000 (date 2026-06-03)
Problem Types: CWE-367 | CWE-367 CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 3.1 | LOW | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N |
| 3.1 | [email protected] | Secondary | 2.2 | LOW | CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:N |
| 3.1 | CNA | DECLARED | 2.2 | LOW | CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:N |
| 2.0 | [email protected] | Primary | 3.5 | AV:N/AC:M/Au:S/C:P/I:N/A:N |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
HighPrivileges Required
LowUser Interaction
NoneScope
UnchangedConfidentiality
LowIntegrity
NoneAvailability
NoneCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
CVSS v2.0 Breakdown
Access Vector
NetworkAccess Complexity
MediumAuthentication
SingleConfidentiality
PartialIntegrity
NoneAvailability
NoneAV:N/AC:M/Au:S/C:P/I:N/A:N
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Kubernetes | Kubernetes | 1.21.0 | All | All | All |
| Application | Kubernetes | Kubernetes | All | All | All | All |
| Application | Kubernetes | Kubernetes | All | All | All | All |
| Application | Kubernetes | Kubernetes | All | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Kubernetes | Kubernetes | affected * semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| [Security Advisory] CVE-2020-8562: Bypass of Kubernetes API Server proxy TOCTOU | af854a3a-2127-422b-91ae-364da2661108 | groups.google.com | Mailing List, Third Party Advisory |
| CVE-2020-8562 Kubernetes Vulnerability in NetApp Products | NetApp Product Security | af854a3a-2127-422b-91ae-364da2661108 | security.netapp.com | Third Party Advisory |
| kubernetes.io/blog/2026/05/26/reconciling-unfixed-kubernetes-cves | [email protected] | kubernetes.io | |
| CVE-2020-8562: Bypass of Kubernetes API Server proxy TOCTOU · Issue #101493 · kubernetes/kubernetes · GitHub | af854a3a-2127-422b-91ae-364da2661108 | github.com | Issue Tracking, Mitigation, Third Party Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Javier Provecho (en)
Additional Advisory Data
Workarounds
CNA: If this issue affects your clusters’ control planes, you can use dnsmasq for name resolution and configure the min-cache-ttl and neg-ttl parameters to a low non-zero value to enforce cached replies for proxied connections
Legacy QID Mappings
- 377835 Bypass of Kubernetes API Server Proxy Vulnerability