Remote UDP DoS by sending multiple DNS Cookie options (CVE-2026-19401) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-19401

Remote UDP DoS by sending multiple DNS Cookie options

Answer in brief

CVE-2026-19401 records a Unknown severity vulnerability in Remote UDP DoS by sending multiple DNS Cookie options. The current sources do not mark it as known exploited. The current feed maps NLnet Labs/NSD (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 26, 2026Updated Aug 26, 2026Source checked Aug 26, 2026First seen by HOL Aug 26, 2026Material review Aug 26, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps NLnet Labs/NSD (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
NLnet Labs/NSDgeneric	>=4.3.7 <4.15.1	4.15.1

Recommended response

Check inventory. Check lockfiles and deployed manifests for NLnet Labs/NSD.
Review the reported fix. Update NLnet Labs/NSD to 4.15.1 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 26, 2026

Sources and claim methodology

Source referencenlnetlabs.nl

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.