---
id: CVE-2021-25736
aliases:
  - GHSA-35c7-w35f-xwgh
  - GO-2023-2159
title: Kube-proxy may unintentionally forward traffic
summary: Kube-proxy may unintentionally forward traffic
severity: medium
cvss: 5.8
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:N/A:N'
vendor: kubernetes
product: k8s.io/kubernetes
ecosystem: go
affected:
  - k8s.io/kubernetes < 1.21.0
patched:
  - k8s.io/kubernetes 1.21.0
published: '2023-10-30'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:03.384919778Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-35c7-w35f-xwgh'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-25736'
  - url: 'https://github.com/kubernetes/kubernetes/pull/99958'
  - url: >-
      https://github.com/kubernetes/kubernetes/commit/b014610de3e5cf1bb0f7844b5758d29fc18b75e6
  - url: 'https://github.com/kubernetes/kubernetes'
  - url: >-
      https://groups.google.com/g/kubernetes-security-announce/c/lIoOPObO51Q/m/O15LOazPAgAJ
  - url: 'https://security.netapp.com/advisory/ntap-20231221-0003'
tags:
  - osv
  - go
epss: 0.00915
epssPercentile: 0.58492
ingestedAt: '2026-09-12T03:13:01.747Z'
---

## Overview

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 packages

- `k8s.io/kubernetes < 1.21.0`

## Remediation

Upgrade to a patched release:

- `k8s.io/kubernetes 1.21.0`