CVE-2021-36754 Scanner

PowerDNS Authoritative Server is a high-performance DNS server software used by enterprises, hosting providers, and network administrators to manage domain name resolution. It supports advanced features like DNSSEC, zone transfers, and multi-tenancy, making it a critical component in many network infrastructures. The server handles millions of DNS queries daily, ensuring reliable domain resolution for users and services.

CVE-2021-36754 is a Denial of Service (DoS) vulnerability that arises from improper validation of DNS query types. Specifically, the server fails to handle a query with QTYPE 65535 correctly, leading to a crash when processing such malformed requests. This flaw exists in versions 4.5.0 to 4.5.1, where the code does not sanitize or reject this unusual QTYPE value.

The vulnerability is triggered by sending a DNS query with QTYPE 65535 to the PowerDNS Authoritative Server. The server's parser attempts to process this invalid type without proper bounds checking, causing a segmentation fault or memory corruption. This can be exploited remotely without authentication, making it a serious threat to availability.

If exploited, an attacker can crash the PowerDNS Authoritative Server, causing a complete denial of service for all domains it serves. This disrupts DNS resolution for users, potentially leading to service outages, loss of revenue, and reputational damage. Organizations relying on this server for critical operations face significant downtime risks.