High

Windows Kernel Heap-Based Buffer Overflow Privilege Escalation

IdentifiersCVE-2026-21245CWE-122· Heap-based Buffer Overflow

CVE-2026-21245 is a heap-based buffer overflow in the Windows Kernel. The available content states that the flaw allows an authorized attacker to elevate privileges locally. No additional public technical detail is provided in the supplied content regarding the specific vulnerable kernel component, function, code path, or triggering input beyond the fact that the memory corruption occurs on the heap within the Windows Kernel.

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 elevation of privilege in Windows. An attacker who already has authorized local access could leverage the heap-based buffer overflow to execute with higher privileges in the context of the Windows Kernel, potentially leading to full system compromise.

Mitigation

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

No vulnerability-specific mitigation is provided in the supplied content. In the absence of a patch, reduce exposure by limiting local access to trusted users, minimizing the ability for untrusted code to execute locally, and applying least-privilege controls until the Microsoft update can be deployed.

Remediation

Patch, then assume compromise.

Apply the Microsoft security update that addresses CVE-2026-21245 for affected Windows versions. The supplied content indicates Microsoft released February 2026 security updates and recommends prompt installation of patches for supported product versions, with verification through Windows Update, Update History, or the Microsoft Update Catalog if necessary.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

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 11 24h2operating_system

Microsoft CorporationWindows 11 25h2operating_system

Microsoft CorporationWindows 11 26h1operating_system

Microsoft CorporationWindows Server 2025operating_system

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

ACTIVITY FEED

Recent activity

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

5 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 privilege escalation vulnerability affecting the Windows Kernel.

bleeping computerNews

Feb 10, 2026

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

An elevation of privilege vulnerability in Windows Kernel (no additional details provided in the content).

zerodayinitiative blogNews

Feb 10, 2026

Zero Day Initiative - The February 2026 Security Update Review

An elevation of privilege vulnerability in the Windows Kernel.

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 activity2

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

EXTERNAL REFERENCES

MITRE CVE

cve.org · CVE-2026-21245

NVD

nvd.nist.gov/vuln/detail/CVE-2026-21245

MITRE CWE · CWE-122

Heap-based Buffer Overflow

Vendor Advisory

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21245