{"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":0.58668,"ingestedAt":"2026-09-12T03:13:01.747Z","slug":"CVE-2021-25736","body":"## Overview\n\nKube-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 \nwhere the LoadBalancer controller sets the `status.loadBalancer.ingress[].ip` field are unaffected.\n\n## Affected packages\n\n- `k8s.io/kubernetes < 1.21.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `k8s.io/kubernetes 1.21.0`","depth":"sunlit","depthScore":32,"depthScoreParts":{"impact":31.9,"likelihood":0.2,"exploitation":0,"ransomware":0},"changes":[]}