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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
NLnet Labs NSD unaffected
Version Status Constraints
4.3.7 affected < 4.15.1

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Project Subscriptions

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Advisories

No advisories yet.

Fixes

Solution

This issue is fixed in 4.15.1 and all later versions.

Workaround

No workaround given by the vendor.

References
Link Providers
https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-19401.txt cve-icon
History

Wed, 26 Aug 2026 08:45:00 +0000

Type Values Removed Values Added
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.
Title Remote UDP DoS by sending multiple DNS Cookie options
Weaknesses CWE-400
CWE-617
References
Metrics cvssV4_0

{'score': 8.2, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: NLnet Labs

Published:

Updated: 2026-08-26T08:44:08.078Z

Reserved: 2026-08-10T07:31:26.962Z

Link: CVE-2026-19401

cve-icon Vulnrichment

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cve-icon NVD

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cve-icon Redhat

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cve-icon OpenCVE Enrichment

Updated: 2026-08-26T09:30:04Z

Weaknesses