CVE-2021-25736

Windows kube-proxy LoadBalancer contention

MEDIUM
6.3
CVSS Score
Published: October 30, 2023 at 02:19 AM UTC
Updated: June 17, 2026 at 03:42 AM UTC
1 product affected across 1 vendorKubernetes· also runs on 1 platform

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Severity
MEDIUM6.3
Exploit prediction
EPSS 0.9%
SSVC
No known exploit

Description

Kube-proxy on Windows can unintentionally forward traffic to local processes listening on the same port (“spec.ports[*].port”) as a LoadBalancer Service when the LoadBalancer controller does not set the “status.loadBalancer.ingress[].ip” field. Clusters where the LoadBalancer controller sets the “status.loadBalancer.ingress[].ip” field are unaffected.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v ≤ v1.20.51.18.0 ≤ v < 1.18.181.19.0 ≤ v < 1.19.101.20.0 ≤ v < 1.20.6
Affected range stops below 1.18.18, so it looks safe — our inference, not a vendor statement
Affected range stops below 1.19.10, so it looks safe — our inference, not a vendor statement
Affected range stops below 1.20.6, so it looks safe — our inference, not a vendor statement
microsoft-windows (environment)

Runs on — not affected

The affected product only carries this flaw when running on these platforms. The platforms themselves are not vulnerable.

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
HIGH
Privileges
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
NVD-CWE-noinfoCWE-114

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