CVE-2026-13321: DNSSEC Validation Bypass via Out-of-Zone NSEC Next Field

highCVSS 8.6CVE-2026-13321

CSIRTS triage

Other

What: There is a DNSSEC validation bypass vulnerability via the out-of-zone NSEC next field.
Who is affected: Deployments using DNSSEC are affected.
Urgency: Remediation is urgent due to the high severity rating and potential for exploitation.
Action: Implement the recommended security measures as outlined in the advisory.

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

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 8.6
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-13321

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-2026-133210.22% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 12% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-13321	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 DNSSEC Validation Bypass

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.

highCVE-2026-52688: RRSIGs with too few labels can lead to bypass of DNSSEC wildcard validationnvd · 2026-07-23
lowCVE-2026-52686: The issue is a DNSSEC validation bypass where wildcard expansion proofs (NSEC/NSEC3 records) a…nvd · 2026-07-23