CVE-2026-33599

# PoC Concept: Malicious DNS Backend responding to DDR/SVCB import socket # Create a raw socket to simulate a DNS server sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) sock.bind(('0.0.0.0', 53)) print("Listening for DNS queries (simulating rogue backend)...") while True: data, addr = sock.recvfrom(1024) print(f"Received query from {addr}") # Simplified logic: Check if it looks like a DDR query (logic omitted for brevity) # Construct a malicious SVCB response # This is a placeholder for the specific crafted packet structure # that triggers the vulnerability in CVE-2026-33599 # Response header (standard DNS response flags) response_header = b'\x84\x00' # Response, Authoritative # In a real exploit, the payload would be a specifically malformed SVCB record # causing the crash in dnsdist. # Example payload structure (Hypothetical): # Transaction ID + Flags + Questions + Answer RRs + Authority RRs + Additional RRs # Followed by the malformed SVCB record. malicious_payload = data[:2] + response_header + data[4:] + b'\x00' * 10 sock.sendto(malicious_payload, addr)

{"cve": {"id": "CVE-2026-33599", "sourceIdentifier": "[email protected]", "published": "2026-04-22T14:16:54.410", "lastModified": "2026-04-24T18:52:06.127", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "A rogue backend can send a crafted SVCB response to a Discovery of Designated Resolvers request, when requested via either the autoUpgrade (Lua) option to newServer or auto_upgrade (YAML) settings. DDR upgrade is not enabled by default."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L", "baseScore": 3.1, "baseSeverity": "LOW", "attackVector": "ADJACENT_NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 1.6, "impactScore": 1.4}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H", "baseScore": 8.1, "baseSeverity": "HIGH", "attackVector": "ADJACENT_NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-125"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:powerdns:dnsdist:*:*:*:*:*:*:*:*", "versionStartIncluding": "1.9.0", "versionEndExcluding": "1.9.13", "matchCriteriaId": "DCC2DF11-EC5C-4112-90F2-C266CB65D390"}, {"vulnerable": true, "criteria": "cpe:2.3:a:powerdns:dnsdist:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.0.0", "versionEndExcluding": "2.0.4", "matchCriteriaId": "29865EC6-C1A0-40F3-B0BB-7F71F9C1DCB7"}]}]}], "references": [{"url": "https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-04.html", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}