CVE-2026-21245

Local privilege escalation via kernel heap overflow

Published Feb 10, 2026 · Updated Feb 10, 2026

Heap-based buffer overflow in the Microsoft Windows Kernel allows local users with low privileges to elevate privileges on affected systems. Microsoft identifies a heap overflow but does not disclose the kernel routine, input path, or incorrect memory operation that triggers it. Exploitation requires local low-privilege access and can compromise confidentiality, integrity, and availability at the elevated privilege level.

CVSS severity7.8
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Heap-based buffer overflow in the Microsoft Windows Kernel allows local users with low privileges to elevate privileges on affected systems. Microsoft identifies a heap overflow but does not disclose the kernel routine, input path, or incorrect memory operation that triggers it. Exploitation requires local low-privilege access and can compromise confidentiality, integrity, and availability at the elevated privilege level.

The record

CVE
CVE-2026-21245
Published
Feb 10, 2026
Updated
Feb 10, 2026
Vendor
Microsoft
Product
Windows Server 2025 (Server Core installation)
Classifications
CWE-787, CWE-122, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.26100.0 <10.0.26100.32370

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows Server 2025 (Server Core installation)version=10.0.26100.0 <10.0.26100.32370
Microsoft · Windows 11, version 25H2version=10.0.26200.0 <10.0.26200.7840
Microsoft · Windows 11, version 24H2version=10.0.26100.0 <10.0.26100.7840
Microsoft · Windows 11, version 26H1version=10.0.28000.0 <10.0.28000.1575
Microsoft · Windows Server 2025version=10.0.26100.0 <10.0.26100.32370

Published CVSS scores

7.8Microsoft CorporationCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-122Heap-based Buffer Overflow
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo