Vulnerability in Powerdns Dnsdist

CVE-2026-40209

An attacker might be able to cause outgoing TCP connections to backend to be stuck until a timeout occurs instead of being released immediately, by sending IXFR queries. This could be used to cause a denial of service if there is a limit to the number of concurrent connections to this backend, or if the process runs out of file descriptors.

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-2026-40209: 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-2026-40209?
CVE-2026-40209 is a medium-severity vulnerability in Powerdns Dnsdist, classified under Missing Release of Resource after Effective Lifetime. CVSS score: 5.3/10. Published 2026-06-25.
How severe is CVE-2026-40209?
Medium severity. CVSS v3 base score is 5.3 out of 10.