Security readout for executives and security teams
Plain-English summary
This issue affects Kubernetes clusters with Windows kube-proxy in a specific LoadBalancer configuration. Traffic meant for a LoadBalancer Service could be sent to a local Windows process listening on the same port. Clusters whose LoadBalancer controller sets status.loadBalancer.ingress[].ip are described as unaffected.
Executive priority
Treat as a targeted Kubernetes configuration risk, not a broad emergency. Prioritize clusters with Windows nodes and external LoadBalancer Services, especially where sensitive traffic is exposed or controller behavior is unknown.
Technical view
Windows kube-proxy can forward traffic to local processes bound to spec.ports[*].port when a LoadBalancer Service lacks status.loadBalancer.ingress[].ip. The CVSS vector indicates network reachability, high attack complexity, high privileges required, no user interaction, scope change, and high confidentiality impact.
Likely exposure
Exposure is limited to Kubernetes environments using Windows kube-proxy, LoadBalancer Services, and controllers that do not populate status.loadBalancer.ingress[].ip. Linux-only clusters or clusters with ingress IP populated are not indicated as affected by the provided sources.
Exploitation context
The source bundle does not show KEV listing or public active exploitation. Exploitation appears configuration-dependent and requires high privileges per CVSS. The main risk is unintended disclosure through traffic being routed to a local process on a Windows node.
Researcher notes
The provided CVE data names Kubernetes Windows kube-proxy behavior and the ingress IP condition, but does not include affected release ranges or fixed versions. Avoid expanding scope beyond Windows kube-proxy and the stated LoadBalancer status condition.
Mitigation direction
- Check Kubernetes security announcement and vendor guidance for fixed or recommended versions.
- Ensure LoadBalancer controllers populate status.loadBalancer.ingress[].ip where applicable.
- Review Windows nodes for unnecessary local listeners on LoadBalancer Service ports.
- Prioritize remediation for clusters exposing sensitive services through LoadBalancer Services.
- Consult NetApp guidance only if relevant to your Kubernetes distribution or product stack.
Validation and detection
- Inventory Kubernetes clusters using Windows nodes and kube-proxy.
- List LoadBalancer Services and check whether status.loadBalancer.ingress[].ip is populated.
- Identify Windows node processes listening on matching LoadBalancer Service ports.
- Review controller behavior for Services whose ingress IP remains unset.
- Confirm remediation status against Kubernetes and vendor advisories.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CWE-114: Exact CWE lookup
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Open ATT&CK lookupContainer behavior lookup
The affected technology mentions containers, so container-specific ATT&CK technique review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-25736 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:N/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:N/A:N1.34Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.8MediumVector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:N/A:N
Source materials
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Process Control
Process Control represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.