Traefik before 3.7.7 Namespace Confusion via HTTPRoute ExtensionRef

{
  "id": "a35822d07f1dcee77dfdcc02e3efb8110b7dc8b5df3a083e38b994a37eea4669",
  "url": "https://osv.dev/vulnerability/CVE-2026-65601",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Traefik before 3.7.7 Namespace Confusion via HTTPRoute ExtensionRef",
    "summary": "Traefik versions 3.7.0 through 3.7.6 contain a namespace confusion vulnerability in the Kubernetes Gateway API provider. When resolving HTTPRoute.spec.rules[].backendRefs[].filters[].extensionRef, Traefik used the backend Service namespace instead of the HTTPRoute namespace. A low-privileged route author holding a ReferenceGrant for a cross-namespace Service could therefore bind a Traefik Middleware from the backend namespace without a separate grant for that middleware, potentially injecting trusted reverse-proxy identity headers into downstream requests. The issue is fixed in version 3.7.7.",
    "evidence": "osv:CVE-2026-65601",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-65601",
      "aliases": [
        "CVE-2026-65601",
        "GHSA-qq9q-x9w4-chhj",
        "GO-2026-6198"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/traefik/traefik",
              "type": "GIT",
              "events": [
                {
                  "introduced": "04aa6bb4f9776f2ba87e5cd181d250e3610e6419"
                },
                {
                  "fixed": "b2c18b1e39fbe2099e4dce927e4e6e56674ede0f"
                },
                {
                  "fixed": "26c96a3935cafb473f4a5bae1886560d9aa4e4f0"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "3.7.0"
                      },
                      {
                        "fixed": "3.7.7"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "26c96a3935cafb473f4a5bae1886560d9aa4e4f0"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v3.7.4",
            "v3.7.3",
            "v3.7.2",
            "v3.7.1",
            "v3.7.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-65601.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:23.202333446Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/65xxx/CVE-2026-65601.json",
        "https://github.com/traefik/traefik/security/advisories/GHSA-qq9q-x9w4-chhj",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-65601",
        "https://www.vulncheck.com/advisories/traefik-before-namespace-confusion-via-httproute-extensionref",
        "https://github.com/traefik/traefik/commit/26c96a3935cafb473f4a5bae1886560d9aa4e4f0"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-863"
        ],
        "cna_assigner": "VulnCheck",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/65xxx/CVE-2026-65601.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-65601",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 489471,
  "published_at": "2026-07-22T11:21:47.468+00:00"
}