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CVE-2026-77891 Microsoft CVE debrief

An out-of-bounds read vulnerability in Windows DHCP Server allows an authorized attacker to execute code locally. The vulnerability has a CVSS score of 6.4 and a severity of MEDIUM. Microsoft has released a patch for this vulnerability. Affected product deployments should be reviewed for exposure, and patches or mitigations should be applied as necessary. The vulnerability can be exploited by an authorized attacker, which can lead to a compromise of the server and potentially the entire network.

Vendor
Microsoft
Product
Windows 10 Version 1607
CVSS
MEDIUM 6.4
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 security teams should assess exposure and apply patches or mitigations as necessary. They should also verify Windows DHCP Server versions and configurations to ensure they are not vulnerable and monitor Windows DHCP Server for suspicious activity to detect potential attacks. Additionally, security teams should review compensating controls for exposed systems while remediation is

Why it matters

This vulnerability allows an authorized attacker to execute code locally on Windows DHCP Server, which can lead to a compromise of the server and potentially the entire network. Windows DHCP Server administrators and security teams should assess exposure and apply patches or mitigations as necessary.

  • Apply patches for Windows DHCP Server to prevent code execution
  • Verify Windows DHCP Server versions and configurations to ensure they are not vulnerable
  • Monitor Windows DHCP Server for suspicious activity to detect potential attacks

Technical summary

An out-of-bounds read vulnerability in Windows DHCP Server allows an authorized attacker to execute code locally. The vulnerability has a CVSS score of 6.4 and a severity of MEDIUM. This vulnerability affects Windows DHCP Server, and administrators should assess exposure and apply patches or mitigations as necessary. The vulnerability can be exploited through a malicious request to the Windows DHCP Server.

Defensive priority

Apply patches for Windows DHCP Server

Recommended defensive actions

  • Apply patches for Windows DHCP Server
  • Verify Windows DHCP Server versions and configurations
  • Monitor Windows DHCP Server for suspicious activity

Evidence notes

The vulnerability is described in the CVE Program record and the NVD vulnerability detail page. Microsoft has released a patch for this vulnerability.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-77891 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-77891

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

  • CVE-2026-77891 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-77891

    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.