What is CVE-2026-19401?

CVE-2026-19401 is a high-severity vulnerability in Nlnet Labs Nsd, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-08-26.

How severe is CVE-2026-19401?

High severity. CVSS v3 base score is 7.5 out of 10.

Resource exhaustion in Nlnet Labs Nsd

CVE-2026-19401

Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a special crafted message with a specially tuned number of DNS Cookie options (17 when UDP payload size is 512). By continuously crashing the serve childs, the remote client can severely hamper or, when positioned sufficiently close, deny all DNS service.

Vulnerability class: DoS (Denial of Service)

Published 2026-08-26 · last modified 2026-09-08.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.003 (18.9th percentile), scored 2026-10-11.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 19th percentile — 18.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.003 · change: -0.001

Affected products

Weakness classification (CWE)

References

www.nlnetlabs.nl/downloads/nsd/CVE-2026-19401.txt (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-19401?: CVE-2026-19401 is a high-severity vulnerability in Nlnet Labs Nsd, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-08-26.
How severe is CVE-2026-19401?: High severity. CVSS v3 base score is 7.5 out of 10.