We released PowerDNS DNSdist 1.9.10 today, fixing several bugs including a security issue tracked as CVE-2025-30193 where a remote, unauthenticated attacker can cause a denial of service via a crafted TCP connection. The issue was reported to us via our public IRC channel so once it was clear that the issue had a security impact we prepared to release a new version as soon as possible.
While we advise upgrading to a fixed version, a work-around is to temporarily restrict the number of queries that DNSdist is willing to accept over a single incoming TCP connection, via the setMaxTCPQueriesPerConnection directive. Setting it to 50 is a safe choice that does not impact performance in our tests.