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PatchSiren cyber security CVE debrief

CVE-2026-77889 Microsoft CVE debrief

A type confusion vulnerability in Windows DHCP Server allows an unauthorized attacker to deny service over a network. The vulnerability has a CVSS score of 7.5 and is classified as HIGH severity. Microsoft has released a patch for this vulnerability. Affected systems include Windows 10, Windows Server 2012, Windows Server 2016, Windows Server 2019, Windows Server 2022, and Windows Server 2025. The vulnerability can be exploited to deny service over a network. Windows DHCP Server administrators and vulnerability management teams should assess exposure and apply patches immediately. The CVE record and NVD entry provide details on the affected systems and CVSS score.

Vendor
Microsoft
Product
Windows 10 Version 1607
CVSS
HIGH 7.5
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

Windows DHCP Server administrators and vulnerability management teams should assess exposure and apply patches immediately. This includes reviewing and updating vulnerability management processes to ensure timely patching and monitoring Windows DHCP Server installations for potential exploitation attempts. Additionally, administrators should confirm whether affected product deployments exist in managed environments,

Why it matters

A type confusion vulnerability in Windows DHCP Server allows an unauthorized attacker to deny service over a network. Windows DHCP Server administrators and vulnerability management teams should assess exposure and apply patches immediately.

  • Potential denial of service over a network
  • Requires patching to prevent exploitation
  • May require updates to vulnerability management processes

Technical summary

The vulnerability is a type confusion issue in Windows DHCP Server, which can be exploited to deny service over a network. The affected systems include Windows 10, Windows Server 2012, Windows Server 2016, Windows Server 2019, Windows Server 2022, and Windows Server 2025.

Defensive priority

Apply patches immediately, especially for Windows DHCP Server installations.

Recommended defensive actions

  • Apply patches immediately, especially for Windows DHCP Server installations.
  • Review and update vulnerability management processes to ensure timely patching.
  • Monitor Windows DHCP Server installations for potential exploitation attempts.

Evidence notes

The vulnerability is described as a type confusion issue in Windows DHCP Server, which can be exploited to deny service over a network. The CVE record and NVD entry provide details on the affected systems and CVSS score.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-77889 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-77889

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

  • CVE-2026-77889 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-77889

    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.