High

Heap-based Buffer Overflow in Windows Hyper-V

IdentifiersCVE-2026-21248CWE-122· Heap-based Buffer Overflow

CVE-2026-21248 is a heap-based buffer overflow vulnerability in Windows Hyper-V. The available content states that the flaw allows an authorized attacker to execute code locally on affected Windows Hyper-V systems. The vulnerability is described in advisory metadata as a heap-based overflow and is associated with Windows Hyper-V remote code execution, but the specific vulnerable function, code path, trigger condition, and affected Hyper-V component are not provided in the supplied material.

For your environment

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows local code execution on an affected Windows Hyper-V host or context accessible to the attacker. Based on the provided description, exploitation requires an authorized attacker and results in execution of attacker-controlled code, which could enable compromise of the affected system and subsequent actions consistent with code execution in the vulnerable Hyper-V environment.

Mitigation

If you can’t patch tonight, do this now.

No specific mitigation for CVE-2026-21248 is provided in the supplied content. In the absence of a vendor-provided workaround, reduce exposure by limiting local access to authorized and trusted users only, minimizing Hyper-V administrative and guest-management access, and prioritizing patch deployment on affected systems.

Remediation

Patch, then assume compromise.

Apply Microsoft's February 2026 security updates for affected Windows versions and Hyper-V components. The supplied content indicates Microsoft released patches for supported product versions and recommends prompt installation, with verification via Windows Update, Update History, or, if necessary, deployment of standalone packages from the Microsoft Update Catalog.

PUBLIC EXPLOITS

Exploits

No valid public exploits. Mallory filtered out 1 candidate as fakes, detection scripts, or README-only repos.

VALID 0 / 1 TOTALView more in app

All candidate exploits were filtered out by Mallory's validation.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

Microsoft CorporationWindows 10 1607operating_system

Microsoft CorporationWindows 10 1809operating_system

Microsoft CorporationWindows 10 21h2operating_system

Microsoft CorporationWindows 10 22h2operating_system

Microsoft CorporationWindows 11 23h2operating_system

Microsoft CorporationWindows 11 24h2operating_system

Microsoft CorporationWindows 11 25h2operating_system

Microsoft CorporationWindows 11 26h1operating_system

Microsoft CorporationWindows Server 2016operating_system

Microsoft CorporationWindows Server 2019operating_system

Microsoft CorporationWindows Server 2022operating_system

Microsoft CorporationWindows Server 2022 23h2operating_system

Microsoft CorporationWindows Server 2025operating_system

Microsoft CorporationWindows Server 23h2operating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

8 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

8 SOURCESView more in app

nsfocus globalNews

Mar 4, 2026

Microsoft’s February Security Update of High-Risk Vulnerability Notice for Multiple Products - NSFOCUS, Inc., a global network and cyber security leader, protects enterprises and carriers from advanced cyber attacks.

A remote code execution vulnerability affecting Windows Hyper-V.

bleeping computerNews

Feb 10, 2026

Microsoft February 2026 Patch Tuesday fixes 6 zero-days, 58 flaws

A remote code execution vulnerability in Windows Hyper-V (no additional details provided in the content).

zerodayinitiative blogNews

Feb 10, 2026

Zero Day Initiative - The February 2026 Security Update Review

A remote code execution vulnerability in Windows Hyper-V.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity4

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES

MITRE CVE

cve.org · CVE-2026-21248

NVD

nvd.nist.gov/vuln/detail/CVE-2026-21248

MITRE CWE · CWE-122

Heap-based Buffer Overflow

Vendor Advisory

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21248