ghsa-5mq7-rwhj-4fh9

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "<= 4.2.0",
        "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-5mq7-rwhj-4fh9/GHSA-5mq7-rwhj-4fh9.json"
      },
      "package": {
        "ecosystem": "NuGet",
        "name": "Steeltoe.Security.Authorization.Certificate",
        "purl": "pkg:nuget/Steeltoe.Security.Authorization.Certificate"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.0.0",
        "4.0.0-beta1",
        "4.0.0-rc1",
        "4.1.0",
        "4.2.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-81868"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-288",
      "CWE-295"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-17T20:30:58Z",
    "nvd_published_at": "2026-09-17T16:17:47Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nWhen Steeltoe's certificate-based authorization (`UseCertificateAuthorization`) is configured, the default configuration of the middleware relies on the `X-Client-Cert` HTTP header to identify the client certificate, without verifying private-key possession. This header is not stripped by common Cloud Foundry routers (like Gorouter or Envoy) on inbound requests.\n\n### Impact\n\nAn attacker who obtains the public certificate of an application instance in the target organization or space can spoof the `X-Client-Cert` header. This allows the attacker to bypass `SameOrg` and `SameSpace` authorization policies, granting unauthorized access to protected endpoints for the duration of the certificate's validity period.\n\n### Affected configuration\n\n- The application uses `AddOrgAndSpacePolicies()` and `UseCertificateAuthorization()` for inter-service authorization.\n- Inbound requests are not restricted to a known trusted proxy source IP.\n- The application's endpoints are network-accessible to the attacker (e.g., exposed to the internet via a public Cloud Foundry route, or the attacker has access to the internal Cloud Foundry network).\n\n### Mitigations\n\nIf an immediate upgrade to a patched version is not possible:\n\n- Restrict `UseCertificateForwarding` to trusted proxy source IPs using `ForwardedHeadersOptions.KnownProxies` and `KnownNetworks`.\n- Change the forwarding header to `X-Forwarded-Client-Cert` so that Cloud Foundry Gorouter and Envoy header stripping mechanisms apply to inbound untrusted requests.\n- Add a secondary authorization layer (e.g., a shared secret or mutual TLS at the proxy layer) for sensitive endpoints.\n- Ensure the application is not bound to a public route unless explicitly required. Use Cloud Foundry internal routes (e.g., `.apps.internal`) and container-to-container network policies to strictly limit network access to intended internal clients.",
  "id": "GHSA-5mq7-rwhj-4fh9",
  "modified": "2026-09-17T20:45:06.060192758Z",
  "published": "2026-09-17T20:30:58Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/SteeltoeOSS/security-advisories/security/advisories/GHSA-5mq7-rwhj-4fh9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-81868"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SteeltoeOSS/Steeltoe/commit/b626ef3d60aaf19c68eeeed5ee81045406c8c6d0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SteeltoeOSS/Steeltoe/releases/tag/4.3.0"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/SteeltoeOSS/security-advisories"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Steeltoe: Header-forwarded client cert lacks proof of private-key possession"
}