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CVE-2026-26156 Microsoft CVE debrief

A heap-based buffer overflow vulnerability in Windows Hyper-V allows an unauthorized attacker to execute code locally. Multiple Windows versions and server releases are affected, including Windows 10, Windows 11, and Windows Server 2016 through 2025. This vulnerability is particularly concerning due to its potential for remote code execution, which could lead to significant operational impacts if exploited. Defenders should assess their exposure, especially for systems exposed to untrusted networks or with remote access capabilities, and prioritize patching accordingly. The vulnerability's severity and potential impact necessitate immediate attention from defenders responsible for

Vendor
Microsoft
Product
Windows 10 Version 1607
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-14
Original CVE updated
2026-10-15
Advisory published
2026-04-14
Advisory updated
2026-10-15

Who should care

Defenders responsible for Windows systems, especially those with Hyper-V enabled or exposed to untrusted networks, should assess their exposure and prioritize patching.

Why it matters

CVE-2026-26156 is a high-severity vulnerability in Windows Hyper-V that allows remote code execution. Defenders should prioritize patching vulnerable systems, especially those exposed to untrusted networks or with remote access capabilities, to prevent potential exploitation.

  • Remote code execution on vulnerable systems
  • Potential lateral movement within networks
  • Elevation of privileges on affected systems
  • Data breaches or system compromise

Technical summary

The vulnerability is a heap-based buffer overflow in Windows Hyper-V that allows an unauthorized attacker to execute code locally. Affected versions include Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 21H2, Windows 10 Version 22H2, Windows 11 version 23H2, Windows 11 Version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1, Windows Server 2016, Windows Server 2016 (Server Core installation), Windows Server 2019, Windows Server 2019 (Server Core installation), Windows Server 2022, Windows Server 2022, 23H2 Edition (Server Core installation), Windows Server 2025, and Windows Server 2025 (Server Core installation).

Defensive priority

Defenders should prioritize patching vulnerable systems, especially those exposed to untrusted networks or with remote access capabilities.

Recommended defensive actions

  • Patch vulnerable Windows systems, especially those exposed to untrusted networks or with remote access capabilities.
  • Verify and apply Microsoft's security updates for affected Windows versions.
  • Monitor systems for unusual activity indicative of potential exploitation.

Evidence notes

The CVE Program and NVD provide official records of the vulnerability. Microsoft has released a patch for the vulnerability. The vulnerability is a heap-based buffer overflow in Windows Hyper-V that allows an unauthorized attacker to execute code locally. Affected versions include Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 21H2, Windows 10 Version 22H2, Windows 11 version 23H2, Windows 11 Version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2, Windows

Sources and references

Verified primary and authoritative sources

  • CVE-2026-26156 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-26156

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

  • CVE-2026-26156 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-26156

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

Supplemental references

  • Windows Hyper-V Remote Code Execution Vulnerability

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/26xxx/CVE-2026-26156.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26156

    Supplemental source - vendor-advisory, patch

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.