CVE-2026-44621: Libunbound applications configured with 'unwanted-reply-threshold' could eventually be abruptly terminated

mediumCVSS 5.9CVE-2026-44621

CSIRTS triage

vendor: Libunbound product: Libunbound Denial of service

What: Applications configured with 'unwanted-reply-threshold' could eventually be abruptly terminated.
Who is affected: Applications using Libunbound with the specified configuration.
Urgency: Remediation is medium urgency due to the medium severity and potential for denial of service.
Action: Review and adjust the unwanted-reply-threshold configuration.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 5.9
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-44621

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-446210.25% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 16% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-44621	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Libunbound applications configured

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

mediumCVE-2026-44621: With NLnet Labs Unbound up to and including version 1.25.1, applications using libunbound and …nvd · 2026-07-22