CVE-2026-19401

High

Description

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.

SeverityHigh

CVSS7.5

Exploit probability40. percentile0.5%

ProductNlnetlabs Nsd

PublishedAug 26, 2026

First seenAug 26, 2026

Weakness typeCWE-617CWE-617 CWE-400Uncontrolled resource consumption

How to fix

Update

nlnetlabs nsd4.15.1 or later

Vendor advisories

nlnetlabs.nl/downloads/nsd/CVE-2026-19401.txt

Affected products

Product	Affected versions	Fixed in
nlnetlabs nsd	4.3.7 ≤ v < 4.15.1	4.15.1

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