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CVE-2026-77499 Microsoft CVE debrief

A type confusion vulnerability in Windows DHCP Server allows an unauthorized attacker to deny service over a network. This CVE was published on 2026-09-08T18:20:36.437Z and was last modified on 2026-09-16T15:10:18.860Z. The vulnerability affects Windows DHCP Server installations, potentially leading to service disruptions. Defenders should verify exposure, apply patches provided by Microsoft, and monitor network environments for unauthorized access attempts. The CVE record and NVD detail page provide information on the vulnerability, including its CVSS score of 7.5 and severity of HIGH.

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

Defenders responsible for Windows DHCP Server installations, network administrators, and incident response teams should be aware of this vulnerability and take necessary actions to verify exposure and apply patches.

Why it matters

CVE-2026-77499 is a type confusion vulnerability in Windows DHCP Server that allows an unauthorized attacker to deny service over a network. Defenders should prioritize verifying exposure, applying patches, and monitoring network environments to prevent potential service disruptions.

  • Potential service disruption due to unauthorized access
  • Need to verify exposure of Windows DHCP Server installations
  • Priority to apply patches provided by Microsoft
  • Monitoring network environments for unauthorized access attempts

Technical summary

The vulnerability is caused by a type confusion issue in Windows DHCP Server, which allows an unauthorized attacker to deny service over a network. The CVSS vector for this vulnerability is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. This issue impacts Windows DHCP Server installations, requiring defenders to prioritize verifying exposure, applying patches, and monitoring network environments to prevent potential service disruptions.

Defensive priority

Defenders should prioritize verifying exposure of Windows DHCP Server installations, especially in network environments where unauthorized access could lead to service disruption.

Recommended defensive actions

  • Verify exposure of Windows DHCP Server installations in your environment.
  • Apply the patch provided by Microsoft to vulnerable systems.
  • Monitor network environments for unauthorized access attempts.
  • Review and update incident response plans to address potential service disruptions.

Evidence notes

The CVE record and NVD detail page provide information on the vulnerability, including its CVSS score of 7.5 and severity of HIGH. Microsoft has provided a patch and vendor advisory for this vulnerability.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-77499 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-77499

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

  • CVE-2026-77499 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-77499

    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.