{"id":"CVE-2026-41272","aliases":["GHSA-2x8m-83vc-6wv4"],"url":"https://o3.security/vulnerability/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.","published":"2026-04-23T19:16:08.113Z","modified":"2026-10-28T02:30:33.802952767Z","cvss":{"score":7.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L"},"epss":{"score":0.00258,"percentile":0.17498,"asOf":"2026-08-12"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"flowise","fixedVersion":"3.1.0"},{"ecosystem":"npm","name":"flowise-components","fixedVersion":"3.1.0"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41272.json"},{"type":"ADVISORY","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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:30:33.802952767Z"}}