Traefik v3.7.1 crossProviderNamespaces Bypass via Service Middleware

{
  "id": "a7a1b8fa77e037e033d748735a0f2f0389b7fb3cee22be98992601b9d985bc8b",
  "url": "https://osv.dev/vulnerability/CVE-2026-85594",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Traefik v3.7.1 crossProviderNamespaces Bypass via Service Middleware",
    "summary": "Traefik versions from v3.7.1 fail to enforce crossProviderNamespaces restrictions on the traefik.ingress.kubernetes.io/service.middlewares Service annotation in the Kubernetes Ingress provider. A namespace-limited tenant excluded from the allowlist can attach an operator-owned middleware to its Service, and if that middleware injects backend credentials, recover them at a controlled backend.",
    "evidence": "osv:CVE-2026-85594",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-85594",
      "aliases": [
        "CVE-2026-85594",
        "GHSA-m6wx-622r-48r9"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/traefik/traefik",
              "type": "GIT",
              "events": [
                {
                  "introduced": "fa49e2bcad7ffd8a80accdf1fae1ae480913d93d"
                },
                {
                  "fixed": "faa1eb590646aed94e561e24a59be0c47353ae95"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "3.7.1"
                      },
                      {
                        "last_affected": "3.7.12"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "cpe": "cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "3.7.11"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v3.7.10",
            "v3.7.9",
            "v3.7.8",
            "v3.7.7",
            "v3.7.6",
            "v3.7.5",
            "v3.7.4",
            "v3.7.3",
            "v3.7.2",
            "v3.7.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-85594.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:28.585597301Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/85xxx/CVE-2026-85594.json",
        "https://github.com/traefik/traefik/security/advisories/GHSA-m6wx-622r-48r9",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-85594",
        "https://www.vulncheck.com/advisories/traefik-3.7.1-crossprovidernamespaces-bypass-via-service-middleware"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-639"
        ],
        "cna_assigner": "VulnCheck",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/85xxx/CVE-2026-85594.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-85594",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 495311,
  "published_at": "2026-09-04T11:29:58.771+00:00"
}