Microsoft Windows 10 21H2/10 22H2/10 1809/Server 2019 Ancillary Function Driver for WinSock free of memory not on the heap

CVSS Meta Temp Score
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CTI Interest Score
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7.1$5k-$25k0.00

Summaryinfo

A vulnerability classified as critical was found in Microsoft Windows 10 21H2/10 22H2/10 1809/Server 2019. Affected is an unknown function of the component Ancillary Function Driver for WinSock. The manipulation results in free of memory not on the heap. This vulnerability is identified as CVE-2026-20810. The attack is only possible with local access. There is not any exploit available. A patch should be applied to remediate this issue.

Detailsinfo

A vulnerability was found in Microsoft Windows 10 21H2/10 22H2/10 1809/Server 2019. It has been classified as critical. Affected is an unknown function of the component Ancillary Function Driver for WinSock. The manipulation with an unknown input leads to a free of memory not on the heap vulnerability. CWE is classifying the issue as CWE-590. The product calls free() on a pointer to memory that was not allocated using associated heap allocation functions such as malloc(), calloc(), or realloc(). This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Free of memory not on the heap in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

The weakness was released 01/13/2026 as confirmed security update guide (Website). The advisory is available at msrc.microsoft.com. This vulnerability is traded as CVE-2026-20810. The exploitability is told to be easy. Local access is required to approach this attack. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of 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). If you want to get best quality of vulnerability data, you may have to visit VulDB.

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: Free of memory not on the heap
CWE: CWE-590
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-2026-20810 (🔒)
GCVE (CVE): GCVE-0-2026-20810
GCVE (VulDB): GCVE-100-340746
CERT Bund: WID-SEC-2026-0083 - Microsoft Windows : Mehrere Schwachstellen

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

Entryinfo

Created: 01/13/2026 19:14
Updated: 01/19/2026 10:53
Changes: 01/13/2026 19:14 (36), 01/13/2026 19:17 (33), 01/16/2026 06:14 (11), 01/19/2026 10:53 (7)
Complete: 🔍
Cache ID: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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