GHSA-2X8M-83VC-6WV4

Vulnerability from github – Published: 2026-04-16 21:51 – Updated: 2026-04-18 00:15
VLAI?
Summary
Flowise: SSRF Protection Bypass (TOCTOU & Default Insecure)
Details

Summary

The core security wrappers (secureAxiosRequest and secureFetch) intended to prevent Server-Side Request Forgery (SSRF) contain multiple logic flaws. These flaws allow attackers to bypass the allow/deny lists via DNS Rebinding (Time-of-Check Time-of-Use) or by exploiting the default configuration which fails to enforce any deny list.

Details

The flaws exist in packages/components/src/httpSecurity.ts.

Default Insecure: If process.env.HTTP_DENY_LIST is undefined, checkDenyList returns immediately, allowing all requests (including localhost).

DNS Rebinding (TOCTOU): The function performs a DNS lookup (dns.lookup) to validate the IP, and then the HTTP client performs a new lookup to connect. An attacker can serve a valid IP first, then switch to an internal IP (e.g., 127.0.0.1) for the second lookup.

PoC

Ensure HTTP_DENY_LIST is unset (default behavior).

Use any node utilizing secureFetch to access http://127.0.0.1.

Result: Request succeeds.

Scenario 2: DNS Rebinding

Attacker controls domain attacker.com and a custom DNS server.

Configure DNS to return 1.1.1.1 (Safe IP) with TTL=0 for the first query.

Configure DNS to return 127.0.0.1 (Blocked IP) for subsequent queries.

Flowise validates attacker.com -> 1.1.1.1 (Allowed).

Flowise fetches attacker.com -> 127.0.0.1 (Bypass).

Run the following for manual verification 

// PoC for httpSecurity.ts Bypasses
import * as dns from 'dns/promises';

// Mocking the checkDenyList logic from Flowise
async function checkDenyList(url: string) {
    const deniedIPs = ['127.0.0.1', '0.0.0.0']; // Simplified deny list logic

    if (!process.env.HTTP_DENY_LIST) {
        console.log(\"⚠️  HTTP_DENY_LIST not set. Returning allowed.\");
        return; // Vulnerability 1: Default Insecure
    }

    const { hostname } = new URL(url);
    const { address } = await dns.lookup(hostname);

    if (deniedIPs.includes(address)) {
        throw new Error(`IP ${address} is denied`);
    }
    console.log(`✅ IP ${address} allowed check.`);
}

async function runPoC() {
    console.log(\"--- Test 1: Default Configuration (Unset HTTP_DENY_LIST) ---\");
    // Ensure env var is unset
    delete process.env.HTTP_DENY_LIST;
    try {
        await checkDenyList('http://127.0.0.1');
        console.log(\"[PASS] Default config allowed localhost access.\");
    } catch (e) {
        console.log(\"[FAIL] Blocked:\", e.message);
    }

    console.log(\"\
--- Test 2: 'private' Keyword Bypass (Logic Flaw) ---\");
    process.env.HTTP_DENY_LIST = 'private'; // User expects this to block localhost
    try {
        await checkDenyList('http://127.0.0.1');
        // In real Flowise code, 'private' is not expanded to IPs, so it only blocks the string \"private\"
        console.log(\"[PASS] 'private' keyword failed to block localhost (Mock simulation).\");
    } catch (e) {
        console.log(\"[FAIL] Blocked:\", e.message);
    }
}

runPoC();

Impact

Confidentiality: High (Access to internal services if protection is bypassed).

Integrity: Low/Medium (If internal services allow state changes via GET).

Availability: Low.

Severity ?
7.1 (High)
CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.0.13"
      },
      "package": {
        "ecosystem": "npm",
        "name": "flowise"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.0.13"
      },
      "package": {
        "ecosystem": "npm",
        "name": "flowise-components"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-918",
      "CWE-367"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-16T21:51:00Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\nThe core security wrappers (secureAxiosRequest and secureFetch) intended to prevent Server-Side Request Forgery (SSRF) contain multiple logic flaws. These flaws allow attackers to bypass the allow/deny lists via DNS Rebinding (Time-of-Check Time-of-Use) or by exploiting the default configuration which fails to enforce any deny list.\n\n\n### Details\nThe flaws exist in `packages/components/src/httpSecurity.ts`.\n\nDefault Insecure: If process.env.HTTP_DENY_LIST is undefined, checkDenyList returns immediately, allowing all requests (including localhost).\n\nDNS Rebinding (TOCTOU): The function performs a DNS lookup (dns.lookup) to validate the IP, and then the HTTP client performs a new lookup to connect. An attacker can serve a valid IP first, then switch to an internal IP (e.g., `127.0.0.1`) for the second lookup.\n\n\n### PoC\nEnsure `HTTP_DENY_LIST` is unset (default behavior).\n\nUse any node utilizing secureFetch to access `http://127.0.0.1`.\n\nResult: Request succeeds.\n\n#### Scenario 2: DNS Rebinding\n\nAttacker controls domain attacker.com and a custom DNS server.\n\nConfigure DNS to return `1.1.1.1` (Safe IP) with TTL=0 for the first query.\n\nConfigure DNS to return `127.0.0.1` (Blocked IP) for subsequent queries.\n\nFlowise validates `attacker.com` -\u003e `1.1.1.1` (Allowed).\n\nFlowise fetches `attacker.com` -\u003e `127.0.0.1` (Bypass).\n\nRun the following for manual verification \n\n```ts\n// PoC for httpSecurity.ts Bypasses\nimport * as dns from \u0027dns/promises\u0027;\n\n// Mocking the checkDenyList logic from Flowise\nasync function checkDenyList(url: string) {\n    const deniedIPs = [\u0027127.0.0.1\u0027, \u00270.0.0.0\u0027]; // Simplified deny list logic\n\n    if (!process.env.HTTP_DENY_LIST) {\n        console.log(\\\"\u26a0\ufe0f  HTTP_DENY_LIST not set. Returning allowed.\\\");\n        return; // Vulnerability 1: Default Insecure\n    }\n\n    const { hostname } = new URL(url);\n    const { address } = await dns.lookup(hostname);\n\n    if (deniedIPs.includes(address)) {\n        throw new Error(`IP ${address} is denied`);\n    }\n    console.log(`\u2705 IP ${address} allowed check.`);\n}\n\nasync function runPoC() {\n    console.log(\\\"--- Test 1: Default Configuration (Unset HTTP_DENY_LIST) ---\\\");\n    // Ensure env var is unset\n    delete process.env.HTTP_DENY_LIST;\n    try {\n        await checkDenyList(\u0027http://127.0.0.1\u0027);\n        console.log(\\\"[PASS] Default config allowed localhost access.\\\");\n    } catch (e) {\n        console.log(\\\"[FAIL] Blocked:\\\", e.message);\n    }\n\n    console.log(\\\"\\\n--- Test 2: \u0027private\u0027 Keyword Bypass (Logic Flaw) ---\\\");\n    process.env.HTTP_DENY_LIST = \u0027private\u0027; // User expects this to block localhost\n    try {\n        await checkDenyList(\u0027http://127.0.0.1\u0027);\n        // In real Flowise code, \u0027private\u0027 is not expanded to IPs, so it only blocks the string \\\"private\\\"\n        console.log(\\\"[PASS] \u0027private\u0027 keyword failed to block localhost (Mock simulation).\\\");\n    } catch (e) {\n        console.log(\\\"[FAIL] Blocked:\\\", e.message);\n    }\n}\n\nrunPoC();\n```\n\n\n### Impact\nConfidentiality: High (Access to internal services if protection is bypassed).\n\nIntegrity: Low/Medium (If internal services allow state changes via GET).\n\nAvailability: Low.",
  "id": "GHSA-2x8m-83vc-6wv4",
  "modified": "2026-04-18T00:15:09Z",
  "published": "2026-04-16T21:51:00Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-2x8m-83vc-6wv4"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/FlowiseAI/Flowise"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Flowise: SSRF Protection Bypass (TOCTOU \u0026 Default Insecure)"
}


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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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