CVE-2026-42083: Free5GC PCF Missing Authentication Middleware Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6rgm-gr97-x3j5",
  "modified" : "2026-06-08T23:46:45Z",
  "published" : "2026-05-07T01:58:42Z",
  "aliases" : [ "CVE-2026-42083" ],
  "summary" : "Free5GC PCF: Missing authentication middleware in Npcf_SMPolicyControl allows access to SM policy handlers and disclosure of subscriber SUPI",
  "details" : "### Summary\nPCF Npcf_SMPolicyControl missing authentication middleware allows unauthenticated access to SM policy handlers and disclosure of subscriber SUPI\n### Details\nIn `NewServer()`, the `smPolicyGroup` route group is created and routes are applied without attaching the router authorization middleware. In contrast, other PCF service groups such as `Npcf_PolicyAuthorization` do attach `RouterAuthorizationCheck` before route registration.\n\nBecause the middleware is missing, requests to the following endpoints can reach business logic even when no valid OAuth token is provided:\n\n- `POST /npcf-smpolicycontrol/v1/sm-policies`\n- `GET /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}`\n- `POST /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}/update`\n- `POST /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}/delete`\n\nThis is visible at runtime because unauthenticated requests return business-level responses such as `400` or `404` instead of being rejected with `401` before handler execution. Under valid lab preconditions (existing UE/session context and related policy data), unauthenticated `POST /sm-policies` can succeed with `201`, and unauthenticated `GET /sm-policies/{id}` can succeed with `200` and return policy context containing subscriber identifiers including `supi`.\n\nThe root cause is missing router auth enforcement for `Npcf_SMPolicyControl`. \nUpstream also fixed this by adding `RouterAuthorizationCheck` to `smPolicyGroup` (and `uePolicyGroup`) in free5gc/pcf PR #63.\n\n### PoC\n1. Deploy free5GC with PCF reachable on the SBI network.\n2. Use the PoC against the PCF service **without** an `Authorization` header:\n   ```bash\n   go run /home/ubuntu/free5gc/tools/npcf-smpolicy-noauth-poc/main.go \\\n     --pcf-root /home/ubuntu/free5gc/NFs/pcf \\\n     --pcf-url http://10.100.200.9:8000 \\\n     --timeout 4s\nObserve that unauthenticated requests to Npcf_SMPolicyControl return business responses instead of 401.\n### Impact\n\nThis is an authentication/authorization bypass on a network-accessible SBI service. Any unauthenticated actor able to reach the PCF SBI interface can invoke Npcf_SMPolicyControl handlers directly.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/free5gc/pcf"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.4.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/free5gc/free5gc/security/advisories/GHSA-6rgm-gr97-x3j5"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-42083"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/free5gc/free5gc/issues/844"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/free5gc/pcf/pull/63"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/free5gc/pcf/commit/8c4d457cdf58bb239ee30e88c56b370b22073964"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/free5gc/free5gc"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-862" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-07T01:58:42Z",
    "nvd_published_at" : "2026-05-27T17:16:35Z"
  }
}