Holes in EndpointSlice Validation Enable Host Network Hijack
Priority LOW 25CWE-184Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- High
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Spoofing
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-601.
Summary
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.
Why it matters now
EPSS 0.01326 71st percentileScored 2026-11-07
Fix Fixed k8s.io/kubernetes (Go): 1.18.19, 1.19.11, 1.20.7 +1Red Hat: 1 advisory
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 | up to 1.18.18; up to 1.19.10; up to 1.20.6; up to 1.21.0 | — | No fix listed | CNA |
| — | k8s.io/kubernetes (Go) | 1.16.0 to before 1.18.19 | 1.18.19 | Patch available | GHSA-mfv7-gq43-w965 |
| — | k8s.io/kubernetes (Go) | 1.19.0 to before 1.19.11 | 1.19.11 | Patch available | GHSA-mfv7-gq43-w965 |
| — | k8s.io/kubernetes (Go) | 1.20.0 to before 1.20.7 | 1.20.7 | Patch available | GHSA-mfv7-gq43-w965 |
| — | k8s.io/kubernetes (Go) | 1.21.0 to before 1.21.1 | 1.21.1 | Patch available | GHSA-mfv7-gq43-w965 |
- Kubernetes VendorKubernetes Affected up to 1.18.18; up to 1.19.10; up to 1.20.6; up to 1.21.0 Fixed in — No fix listed CNA
- k8s.io/kubernetes (Go) Vendor— Affected 1.16.0 to before 1.18.19 Fixed in 1.18.19 Patch available GHSA-mfv7-gq43-w965
- k8s.io/kubernetes (Go) Vendor— Affected 1.19.0 to before 1.19.11 Fixed in 1.19.11 Patch available GHSA-mfv7-gq43-w965
- k8s.io/kubernetes (Go) Vendor— Affected 1.20.0 to before 1.20.7 Fixed in 1.20.7 Patch available GHSA-mfv7-gq43-w965
- k8s.io/kubernetes (Go) Vendor— Affected 1.21.0 to before 1.21.1 Fixed in 1.21.1 Patch available GHSA-mfv7-gq43-w965
CPE configurations NVD · 2
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:kubernetes:kubernetes:*:*:*:*:*:*:*:* | 1.16.0 to before 1.18.19; 1.19.0 to before 1.19.10; 1.20.0 to before 1.20.7 | Vulnerable | Kubernetes |
| cpe:2.3:a:kubernetes:kubernetes:1.21.0:-:*:*:*:*:*:* | 1.21.0 | Vulnerable | Kubernetes |
- cpe:2.3:a:kubernetes:kubernetes:*:*:*:*:*:*:*:* Versions 1.16.0 to before 1.18.19; 1.19.0 to before 1.19.10; 1.20.0 to before 1.20.7 Vulnerable ·Kubernetes
- cpe:2.3:a:kubernetes:kubernetes:1.21.0:-:*:*:*:*:*:* Versions 1.21.0 Vulnerable ·Kubernetes
Remediation
- Fix · GHSA-mfv7-gq43-w965 k8s.io/kubernetes (Go) Fixed in 1.18.19 Advisory →
- Fix · GHSA-mfv7-gq43-w965 k8s.io/kubernetes (Go) Fixed in 1.19.11 Advisory →
- Fix · GHSA-mfv7-gq43-w965 k8s.io/kubernetes (Go) Fixed in 1.20.7 Advisory →
- Fix · GHSA-mfv7-gq43-w965 k8s.io/kubernetes (Go) Fixed in 1.21.1 Advisory →
Red Hat 1 advisory
- RHSA-2021:2437 Released 2021-07-27 · Red Hat rating ModerateOpenShift Container Platform 4.8.2 packages and security update
- Red Hat OpenShift Container Platform 4.8 afterburn-5.0.0-1.rhaos4.8.el8, atomic-openshift-service-idler-4.8.0-202106281541.p0.git.39cfc66.assembly.stream.el8, butane-0.12.1-1.rhaos4.8.el8 +47
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 4.8 | Fixed | RHSA-2021:2437 |
Not affected: 2 products
- Red Hat OpenShift Container Platform 3.11
- Red Hat OpenShift Container Platform 4.8
Timeline
- 2026-10-02 Threatist record created from CVE-2021-25737
- 2026-10-03 Alias added: GHSA-mfv7-gq43-w965
References
Advisory 3
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-2021-25737 · CVE Program
- CVE-2021-25737 · NVD
- FIRST EPSS
- GHSA-mfv7-gq43-w965 · GitHub Advisory Database · CC BY 4.0
- CVE-2021-25737 · 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