Microsoft Windows up to Server 2025 Kernel toctou

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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7.1$5k-$25k0.00

Summaryinfo

A vulnerability classified as critical has been found in Microsoft Windows. This impacts an unknown function of the component Kernel. The manipulation leads to toctou. This vulnerability is referenced as CVE-2026-20809. The attack can only be performed from a local environment. No exploit is available. It is suggested to install a patch to address this issue.

Detailsinfo

A vulnerability was found in Microsoft Windows and classified as critical. This issue affects some unknown processing of the component Kernel. The manipulation with an unknown input leads to a toctou vulnerability. Using CWE to declare the problem leads to CWE-367. The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Time-of-check time-of-use (toctou) race condition in Windows Kernel Memory allows an authorized attacker to elevate privileges locally.

The weakness was published 01/13/2026 as confirmed security update guide (Website). The advisory is shared at msrc.microsoft.com. The identification of this vulnerability is CVE-2026-20809. The exploitation is known to be easy. An attack has to be approached locally. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 01/19/2026).

Applying a patch is able to eliminate this problem. A possible mitigation has been published immediately after the disclosure of the vulnerability.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-0083). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

  • Microsoft Windows 11
  • Microsoft Windows Server 2016
  • Microsoft Windows 10
  • Microsoft Windows Server 2019
  • Microsoft Windows Server 2022
  • Microsoft Windows Server 2025
  • Microsoft Windows Server
  • Microsoft Windows Server 2012
  • Microsoft Windows Server 2012 R2

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.8
VulDB Meta Temp Score: 7.1

VulDB Base Score: 7.8
VulDB Temp Score: 6.8
VulDB Vector: 🔒
VulDB Reliability: 🔍

Vendor Base Score (Microsoft): 7.8
Vendor Vector (Microsoft): 🔒

CNA Base Score: 7.8
CNA Vector (Microsoft): 🔒

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Toctou
CWE: CWE-367 / CWE-362
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Unproven

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

Reaction Time: 🔒
0-Day Time: 🔒
Exposure Time: 🔒

Timelineinfo

01/13/2026 VulDB entry created
01/13/2026 +0 days Advisory disclosed
01/13/2026 +0 days Countermeasure disclosed
01/19/2026 +6 days VulDB entry last update

Sourcesinfo

Vendor: microsoft.com
Product: microsoft.com

Advisory: msrc.microsoft.com
Status: Confirmed

CVE: CVE-2026-20809 (🔒)
GCVE (CVE): GCVE-0-2026-20809
GCVE (VulDB): GCVE-100-340745
CERT Bund: WID-SEC-2026-0083 - Microsoft Windows : Mehrere Schwachstellen

scip Labs: https://www.scip.ch/en/?labs.20161215

Entryinfo

Created: 01/13/2026 19:13
Updated: 01/19/2026 10:53
Changes: 01/13/2026 19:13 (3), 01/13/2026 19:14 (33), 01/13/2026 19:17 (33), 01/16/2026 06:14 (11), 01/19/2026 10:53 (7)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Discussion

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