CVE-2026-33594 Outgoing DoH excessive memory allocation

Medium 5.3 Published 22 Apr 2026 Updated 22 Apr 2026

A remote attacker can cause excessive memory consumption in PowerDNS DNSdist by flooding queries to an overloaded DoH backend, leading to service disruption.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-33594?

CVE-2026-33594 is a medium-severity denial of service vulnerability in PowerDNS DNSdist, published on 22 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

A client can trigger excessive memory allocation by generating a lot of queries that are routed to an overloaded DoH backend, causing queries to accumulate into a buffer that will not be released until the end of the connection.

Weakness: CWE-770

Which versions are affected by CVE-2026-33594?

It affects 1 product.

Products include Powerdns Dnsdist.

How do I fix CVE-2026-33594?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-33594 being exploited?

There is no known exploitation of CVE-2026-33594 in the wild and no public exploit code.

Sources

Also known as DEBIAN-CVE-2026-33594, GHSA-x24g-wfwp-9pcm, UBUNTU-CVE-2026-33594.