CVE-2026-21236Public exploit

SYSTEM privilege escalation via mismatched SAN buffer lengths

Published Feb 10, 2026 · Updated Feb 10, 2026

Heap-based buffer overflow in Microsoft Windows AFD.sys allows local users to elevate privileges through crafted SAN requests. AfdSanConnectHandler copies a user-controlled length of request data into a smaller heap buffer allocated by AfdSuperAccept without reconciling the two lengths. Low-privileged local access and a usable SAN endpoint are required; successful exploitation grants SYSTEM privileges.

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

What happened

Heap-based buffer overflow in Microsoft Windows AFD.sys allows local users to elevate privileges through crafted SAN requests. AfdSanConnectHandler copies a user-controlled length of request data into a smaller heap buffer allocated by AfdSuperAccept without reconciling the two lengths. Low-privileged local access and a usable SAN endpoint are required; successful exploitation grants SYSTEM privileges.

The record

CVE
CVE-2026-21236
Published
Feb 10, 2026
Updated
Feb 10, 2026
Vendor
Microsoft
Product
Windows Server 2019
Classifications
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=10.0.17763.0 <10.0.17763.8389

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows Server 2019version=10.0.17763.0 <10.0.17763.8389
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 Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.8868
Microsoft · Windows 11, version 24H2version=10.0.26100.0 <10.0.26100.7840
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.9200.0 <6.2.9200.25923
Microsoft · Windows Server 2012version=6.2.9200.0 <6.2.9200.25923
Microsoft · Windows 10 Version 21H2version=10.0.19044.0 <10.0.19044.6937
Microsoft · Windows Server 2022, 23H2 Edition (Server Core installation)version=10.0.25398.0 <10.0.25398.2149
Microsoft · Windows Server 2016version=10.0.14393.0 <10.0.14393.8868
Microsoft · Windows 11 Version 22H3version=10.0.22631.0 <10.0.22631.6649
Microsoft · Windows 10 Version 22H2version=10.0.19045.0 <10.0.19045.6937
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.9600.0 <6.3.9600.23022
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <10.0.17763.8389
Microsoft · Windows 11, version 26H1version=10.0.28000.0 <10.0.28000.1575
Microsoft · Windows 11 Version 23H2version=10.0.22631.0 <10.0.22631.6649
Microsoft · Windows 10 Version 1607version=10.0.14393.0 <10.0.14393.8868
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.4773
Microsoft · Windows Server 2025version=10.0.26100.0 <10.0.26100.32370
Microsoft · Windows 10 Version 1809version=10.0.17763.0 <10.0.17763.8389
Microsoft · Windows Server 2012 R2version=6.3.9600.0 <6.3.9600.23022

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 exploitPublished

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1068Exploitation for Privilege Escalation

Public exploit references

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

Technologies

Your stack

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Your stack

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