CVE-2026-41272: Flowise SSRF Protection Bypass (TOCTOU & Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2x8m-83vc-6wv4",
  "modified" : "2026-04-24T21:01:27Z",
  "published" : "2026-04-16T21:51:00Z",
  "aliases" : [ "CVE-2026-41272" ],
  "summary" : "Flowise: SSRF Protection Bypass (TOCTOU & Default Insecure)",
  "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` -> `1.1.1.1` (Allowed).\n\nFlowise fetches `attacker.com` -> `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 'dns/promises';\n\n// Mocking the checkDenyList logic from Flowise\nasync function checkDenyList(url: string) {\n    const deniedIPs = ['127.0.0.1', '0.0.0.0']; // Simplified deny list logic\n\n    if (!process.env.HTTP_DENY_LIST) {\n        console.log(\\\"⚠️  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(`✅ 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('http://127.0.0.1');\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: 'private' Keyword Bypass (Logic Flaw) ---\\\");\n    process.env.HTTP_DENY_LIST = 'private'; // User expects this to block localhost\n    try {\n        await checkDenyList('http://127.0.0.1');\n        // In real Flowise code, 'private' is not expanded to IPs, so it only blocks the string \\\"private\\\"\n        console.log(\\\"[PASS] 'private' 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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "flowise"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.1.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.0.13"
    }
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "flowise-components"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.1.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.0.13"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-2x8m-83vc-6wv4"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-41272"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/FlowiseAI/Flowise"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-367", "CWE-918" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-16T21:51:00Z",
    "nvd_published_at" : "2026-04-23T20:16:15Z"
  }
}