Resource exhaustion in Powerdns Dnsdist

CVE-2026-40211

An attacker can send crafted DNS over HTTP/3 queries, triggering an exception that prevents some buffer from being freed right away. The buffer will be freed at the end of the QUIC connection, but on some setups it might be possible to open enough concurrent DoH3 streams to trigger an out-of-memory condition, resulting in a denial of service.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

EPSS: 0.007 (51.3th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 51.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-40211: held from 0.003 to 0.007.

EPSS over last 30 days · oldest: 0.003 · newest: 0.007 · change: +0.004

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-40211?
CVE-2026-40211 is a medium-severity vulnerability in Powerdns Dnsdist, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 5.3/10. Published 2026-06-25.
How severe is CVE-2026-40211?
Medium severity. CVSS v3 base score is 5.3 out of 10.