What’s Vulnerable › Vulnerabilities

CVE-2021-25737: Holes in EndpointSlice Validation Enable Host Network Hijack

• Severity: medium (CVSS 4.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-09-06 · updated 2026-06-17
• Weakness: CWE-184

Description

A security issue was discovered in Kubernetes where a user may be able to redirect pod traffic to private networks on a Node. Kubernetes already prevents creation of Endpoint IPs in the localhost or link-local range, but the same validation was not performed on EndpointSlice IPs.

Affected products

• Kubernetes: from 1.16.0 before 1.18.19; from 1.19.0 before 1.19.10; from 1.20.0 before 1.20.7; 1.21.0 — fixed in 1.18.19, 1.19.10, 1.20.7

How to fix

Upgrade to a fixed version: Kubernetes 1.18.19, 1.19.10, 1.20.7. Check the vendor advisory for mitigations.

References

• https://github.com/kubernetes/kubernetes/issues/102106
• https://groups.google.com/g/kubernetes-security-announce/c/xAiN3924thY
• https://security.netapp.com/advisory/ntap-20211004-0004/
• https://github.com/kubernetes/kubernetes/issues/102106
• https://groups.google.com/g/kubernetes-security-announce/c/xAiN3924thY
• https://security.netapp.com/advisory/ntap-20211004-0004/

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