PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-70091 Microsoft CVE debrief

A race condition vulnerability in Windows DNS could allow an unauthorized attacker to deny service over a network. This medium-severity vulnerability, tracked as CVE-2026-70091, affects multiple Windows versions and requires immediate attention from system administrators and security teams. The vulnerability exists due to improper synchronization of shared resources in Windows DNS, allowing an attacker to cause a denial of service. Affected versions include Windows 10, Windows Server 2012, 2016, 2019, 2022, and 2025. System administrators and security teams should assess exposure, prioritize patching for affected systems, and monitor DNS services for unusual activity.

Vendor
Microsoft
Product
Windows 10 Version 1607
CVSS
MEDIUM 5.9
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-08
Original CVE updated
2026-09-16
Advisory published
2026-09-08
Advisory updated
2026-09-16

Who should care

System administrators and security teams responsible for Windows systems, particularly those using Windows DNS, should assess exposure and prioritize patching.

Why it matters

CVE-2026-70091 is a medium-severity vulnerability in Windows DNS that could allow an unauthorized attacker to deny service. System administrators and security teams should assess exposure, prioritize patching for affected systems, and monitor DNS services for unusual activity. The vulnerability requires verification of system configurations and patch levels, and potential disruption to network operations should be considered.

  • Denial of service to Windows DNS services
  • Potential disruption to network operations
  • Need for verification of system configurations and patch levels

Technical summary

The vulnerability exists in Windows DNS due to improper synchronization of shared resources, allowing an attacker to cause a denial of service. Affected versions include Windows 10, Windows Server 2012, 2016, 2019, 2022, and 2025. The vulnerability can be exploited by an unauthorized attacker to deny service over a network. System administrators and security teams should assess exposure and prioritize patching for affected systems.

Defensive priority

Medium-priority patching and verification recommended for affected Windows systems.

Recommended defensive actions

  • Apply patches from Microsoft for affected Windows systems
  • Verify system configurations and update vulnerable versions
  • Monitor DNS services for unusual activity

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, but additional information on exploitation or impact is limited. The vulnerability requires verification of system configurations and patch levels, and potential disruption to network operations should be considered. There is no evidence of public exploitation, but defenders should verify system configurations and patch levels to ensure protection.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-70091 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-70091

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-70091 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-70091

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.