A security issue was discovered in Kubernetes where actors that control the responses of MutatingWebhookConfiguration or ValidatingWebhookConfiguration requests are able to redirect kube-apiserver requests to private networks of the apiserver. If that user can view kube-apiserver logs when the log level is set to 10, they can view the redirected responses and headers in the logs.
A workaround or mitigation is available. Apply it until an official patch is released.
CVSS v4.0 Metrics
Exploitability
Attack VectorNetwork
ComplexityLow
RequirementsPresent
PrivilegesHigh
User InteractionNone
Threat
Exploit MaturityPoC
Vulnerable System
ConfidentialityLow
IntegrityNone
AvailabilityNone
Subsequent System
ConfidentialityNone
IntegrityNone
AvailabilityNone
Supplemental
SafetyNegligible
AutomatableYes
RecoveryAutomatic
Value DensityConcentrated
UrgencyMedium
Change Log
| Date | Source | Changes | Score |
|---|
| 2026-07-21 | PoC | E: U→P | 0.5 → 1.2 |
| 2026-07-21 | nvd | patch: Unavailable→Mitigation | 0.5 → 0.5 |
| 2026-07-21 | cve.org | initial, patch: Unavailable | 0.5 |
Affected Software
| Vendor | Product | Version |
|---|
| Kubernetes | Kubernetes | 0 |
| kubernetes | kubernetes | 1.20.11 |
| kubernetes | kubernetes | 1.21.5 |
| kubernetes | kubernetes | 1.22.2 |
Published: 2021-09-20
