In some circumstances, when DNSdist is configured to allow an unlimited number of queries on a single, incoming TCP connection from a client, an attacker can cause a denial of service by crafting a TCP exchange that triggers an exhaustion of the stack and a crash of DNSdist, causing a denial of service.

The remedy is: upgrade to the patched 1.9.10 version.

A workaround is to restrict the maximum number of queries on incoming TCP connections to a safe value, like 50, via the setMaxTCPQueriesPerConnection setting.

We would like to thank Renaud Allard for bringing this issue to our attention.

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE-674

https://dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2025-03.html