CVE-2026-42903: Windows Kerberos Denial of Service Vulnerability

mediumCVSS 6.5CVE-2026-42903

Null pointer dereference in Windows Kerberos allows an authorized attacker to deny service over a network.

CSIRTS triage

vendor: Microsoft product: Windows Kerberos Denial of service

What: Null pointer dereference in Windows Kerberos allows an authorized attacker to deny service over a network.
Who is affected: Authorized users of Windows Kerberos.
Urgency: Remediation is important due to the medium severity and potential for denial of service.
Action: Apply the latest security patch from Microsoft.

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 6.5
Published: 2026-06-09
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42903

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-2026-429030.90% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 56% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-42903	coverage & exploitation status	NVD · CVE.org

Recent advisories for Windows Kerberos Denial

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-2026-42914: Windows Kerberos Denial of Service Vulnerabilitymsrc · 2026-06-09