CriticalCVE-2026-68820

Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability (CVE-2026-68820)

Published 11.08.2026Last modified 26.10.2026In CISA KEV since 11.08.2026Sources: pwn.watch, CVE.org, Msrc Update Guide, BSI

What is affected, what to do

Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

The vulnerability is being actively exploited; treat it as a priority. Update Microsoft Windows 10 Version 1607 to version 10.0.14393.9418, Microsoft Windows 10 Version 1809 to version 10.0.17763.9121, Microsoft Windows 10 Version 21H2 to version 10.0.19044.7663. Immediate actions, mitigation and detection rules are in the runbook below.

Affected: Microsoft Windows 10 Version 1607 lt 10.0.14393.0..10.0.14393.9418
Microsoft Windows 10 Version 1809 lt 10.0.17763.0..10.0.17763.9121
Microsoft Windows 10 Version 21H2 lt 10.0.19044.0..10.0.19044.7663
Microsoft Windows 10 Version 22H2 lt 10.0.19045.0..10.0.19045.7663
Microsoft Windows 11 version 23H2 lt 10.0.22631.0..10.0.22631.7517
Microsoft Windows 11 Version 24H2 lt 10.0.26100.0..10.0.26100.9168
Microsoft Windows 11 Version 25H2 lt 10.0.26200.0..10.0.26200.9168
Microsoft Windows 11 version 26H1 lt 10.0.28000.0..10.0.28000.2704
Microsoft Windows Server 2012 lt 6.2.9200.0..6.2.9200.26280
Microsoft Windows Server 2012 (Server Core installation) lt 6.2.9200.0..6.2.9200.26280
Microsoft Windows Server 2012 R2 lt 6.3.9600.0..6.3.9600.23338
Microsoft Windows Server 2012 R2 (Server Core installation) lt 6.3.9600.0..6.3.9600.23338
Microsoft Windows Server 2016 lt 10.0.14393.0..10.0.14393.9418
Microsoft Windows Server 2016 (Server Core installation) lt 10.0.14393.0..10.0.14393.9418
Microsoft Windows Server 2019 lt 10.0.17763.0..10.0.17763.9121
Microsoft Windows Server 2019 (Server Core installation) lt 10.0.17763.0..10.0.17763.9121
Microsoft Windows Server 2022 lt 10.0.20348.0..10.0.20348.5499
Microsoft Windows Server 2025 lt 10.0.26100.0..10.0.26100.33296
Microsoft Windows Server 2025 (Server Core installation) lt 10.0.26100.0..10.0.26100.33296
Fixed in: Microsoft Windows 10 Version 1607 10.0.14393.9418
Microsoft Windows 10 Version 1809 10.0.17763.9121
Microsoft Windows 10 Version 21H2 10.0.19044.7663
Microsoft Windows 10 Version 22H2 10.0.19045.7663
Microsoft Windows 11 version 23H2 10.0.22631.7517
Microsoft Windows 11 Version 24H2 10.0.26100.9168
Microsoft Windows 11 Version 25H2 10.0.26200.9168
Microsoft Windows 11 version 26H1 10.0.28000.2704
Microsoft Windows Server 2012 6.2.9200.26280
Microsoft Windows Server 2012 (Server Core installation) 6.2.9200.26280
Microsoft Windows Server 2012 R2 6.3.9600.23338
Microsoft Windows Server 2012 R2 (Server Core installation) 6.3.9600.23338
Microsoft Windows Server 2016 10.0.14393.9418
Microsoft Windows Server 2016 (Server Core installation) 10.0.14393.9418
Microsoft Windows Server 2019 10.0.17763.9121
Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.9121
Microsoft Windows Server 2022 10.0.20348.5499
Microsoft Windows Server 2025 10.0.26100.33296
Microsoft Windows Server 2025 (Server Core installation) 10.0.26100.33296

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Metrics

7.0

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: NVD, CVSS v3

7.0

CVSS v3

Severity High on the scale from 0 to 10.

Source: pwn.watch, CVE.org, Msrc Update Guide, BSI

0.3 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 26.2

Show all metrics

Severity: Critical
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 163.65 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 7.0 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 7.0
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 0.3 %; Low — model estimates < 1% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 26.2; Elevated — this CVE ranks above at least 10% of all CVEs scored today.
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: Actively exploited
Published: 11.08.2026
In CISA KEV since The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: 11.08.2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-416

Response and mitigation

Why act now?

Prioritisation rationale

Exploitation requires local access with a valid low-privileged account and has high attack complexity. Statistical models rate the general exploitation likelihood as fairly low, but KEV listing confirms real-world use — typically as the escalation link in a chain that starts with phishing, an infostealer infection or compromised VPN/RDP credentials. Afd.sys is a recurring LPE target, and success yields full SYSTEM control with complete loss of host confidentiality, integrity and availability. CISA currently records no known ransomware use. Treat this as high urgency for terminal servers, VDI and admin workstations, and medium-to-high for the general client fleet; fold it into the next regular patch cycle, but no later than the KEV due date.

01
Runbook step 1
Immediate response (0-24 h)
- Deploy the Microsoft security update: A patch is available from the vendor — look up the fixed build in the MSRC advisory for CVE-2026-68820. CPE data lists the following as affected:
  
  Windows 10 1607 (reference build 10.0.14393.9418)
  
  Windows 10 1809 (10.0.17763.9115)
  
  Windows 10 21H2 (10.0.19044.7663)
  
  Windows 10 22H2 (10.0.19045.7663)
  
  Windows 11 23H2 (10.0.22631.7517)
  
  Windows 11 24H2 (10.0.26100.9106)
  
  Reconcile installed builds via Intune, SCCM/MECM or WSUS reporting against the fixed build in the advisory.
- Patch shared multi-user hosts first: Prioritise RDS/terminal servers, Citrix/VDI pools, jump hosts and PAWs, build servers and shared admin workstations. Many low-privileged users can run code on these systems, and a single SYSTEM compromise exposes every session.
- Check Server editions: Builds 14393 and 17763 correspond to the Windows Server 2016 and 2019 LTSC lines. Confirm in the MSRC advisory whether Server SKUs are listed and include them in the same change if so.
- Fast-track hosts with prior compromise: Patch or isolate endpoints with open EDR alerts (phishing payloads, infostealers, suspicious script execution) from the last 30 days first. This bug is typically used as a second stage after initial access.
- Trim local admin and logon rights: Remove "Allow log on locally" and "Allow log on through Remote Desktop Services" from accounts that don't need interactive access. This shrinks the pool of accounts able to trigger the flaw.
02
Runbook step 2
Mitigation layers
- Configuration: There is no practical workaround for afd.sys. The driver underpins WinSock networking and must not be disabled. Compensating controls therefore focus on stopping exploit execution and containing the blast radius.
- Application control: Run WDAC or AppLocker in enforce mode on multi-user systems. Block unsigned EXE and DLL files from %TEMP%, %APPDATA%, %LOCALAPPDATA%, C:\Users\Public and Downloads folders. Local privilege-escalation exploits are almost always dropped as standalone binaries or loaded reflectively.
- Endpoint hardening: Enable the following ASR rules:
  
  "Block executable files from running unless they meet a prevalence, age, or trusted list criterion"
  
  "Block credential stealing from the Windows local security authority subsystem"
  
  Also enable LSA protection (RunAsPPL) and Credential Guard to make post-escalation credential dumping harder.
- IAM / least privilege: Enforce the tiering model. Domain admins and privileged service accounts must never log on to Tier-1 or Tier-2 hosts; use the Protected Users group to prevent cached credentials from being harvested. Deploy LAPS or Windows LAPS for unique local admin passwords.
- Network segmentation: Limit lateral movement after escalation. Block SMB (445), RDP (3389), WinRM (5985/5986) and RPC (135) between client VLANs via host firewall or network ACL, and allow admin protocols only from the PAW segment.
03
Runbook step 3
Detection rules
- Process lineage (Sysmon EID 1 / Security 4688): Flag SYSTEM-integrity processes whose parent runs at medium or low integrity, or originates from a user-writable path.
  
  Example KQL: DeviceProcessEvents | where ProcessIntegrityLevel == "System" and InitiatingProcessIntegrityLevel in ("Medium","Low") and InitiatingProcessFolderPath has_any (@"\Users\", @"\Temp\", @"\ProgramData\")
- Token abuse: Watch for cmd.exe, powershell.exe or conhost.exe running as SYSTEM without a legitimate parent such as services.exe, svchost.exe or a software-deployment agent. Sigma shape: selection: User|endswith: 'SYSTEM'; Image|endswith: ['\cmd.exe','\powershell.exe']; filter: ParentImage|endswith: ['\services.exe','\svchost.exe','\CcmExec.exe'].
- Failed exploitation attempts: High-complexity use-after-free exploits often crash the host. Hunt the System log for Event ID 1001 (BugCheck) and Event ID 41 (Kernel-Power) where minidump triage points to afd.sys. Repeated bluescreens on a single host are a red flag.
- Post-exploitation signals:
  
  Security 4672 (special privileges assigned) shortly after a type 2/10 logon (4624) by a non-admin account
  
  Sysmon EID 10 accessing lsass.exe (GrantedAccess 0x1010/0x1410)
  
  4697/7045 (new service installed) in the same window
- Binary staging: Sysmon EID 11 for new PE files in user-writable paths, followed by EID 1 with the same hash. Also review EDR telemetry for unsigned processes issuing unusual socket IOCTLs, where your EDR exposes it.

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

Source: pwn.watch, cvelistv5, Microsoft Security Update Guide, NVD (NIST), CISA KEV Catalog, BSI WID Portal, BSI CSAF

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
Microsoft	Windows 10 Version 1607	`10.0.14393.0 – < 10.0.14393.9418`	`10.0.14393.9418`
Microsoft	Windows 10 Version 1809	`10.0.17763.0 – < 10.0.17763.9121`	`10.0.17763.9121`
Microsoft	Windows 10 Version 21H2	`10.0.19044.0 – < 10.0.19044.7663`	`10.0.19044.7663`
Microsoft	Windows 10 Version 22H2	`10.0.19045.0 – < 10.0.19045.7663`	`10.0.19045.7663`
Microsoft	Windows 11 version 23H2	`10.0.22631.0 – < 10.0.22631.7517`	`10.0.22631.7517`
Microsoft	Windows 11 Version 24H2	`10.0.26100.0 – < 10.0.26100.9168`	`10.0.26100.9168`
Microsoft	Windows 11 Version 25H2	`10.0.26200.0 – < 10.0.26200.9168`	`10.0.26200.9168`
Microsoft	Windows 11 version 26H1	`10.0.28000.0 – < 10.0.28000.2704`	`10.0.28000.2704`
Microsoft	Windows Server 2012	`6.2.9200.0 – < 6.2.9200.26280`	`6.2.9200.26280`
Microsoft	Windows Server 2012 (Server Core installation)	`6.2.9200.0 – < 6.2.9200.26280`	`6.2.9200.26280`
Microsoft	Windows Server 2012 R2	`6.3.9600.0 – < 6.3.9600.23338`	`6.3.9600.23338`
Microsoft	Windows Server 2012 R2 (Server Core installation)	`6.3.9600.0 – < 6.3.9600.23338`	`6.3.9600.23338`
Microsoft	Windows Server 2016	`10.0.14393.0 – < 10.0.14393.9418`	`10.0.14393.9418`
Microsoft	Windows Server 2016 (Server Core installation)	`10.0.14393.0 – < 10.0.14393.9418`	`10.0.14393.9418`
Microsoft	Windows Server 2019	`10.0.17763.0 – < 10.0.17763.9121`	`10.0.17763.9121`
Microsoft	Windows Server 2019 (Server Core installation)	`10.0.17763.0 – < 10.0.17763.9121`	`10.0.17763.9121`
Microsoft	Windows Server 2022	`10.0.20348.0 – < 10.0.20348.5499`	`10.0.20348.5499`
Microsoft	Windows Server 2025	`10.0.26100.0 – < 10.0.26100.33296`	`10.0.26100.33296`
Microsoft	Windows Server 2025 (Server Core installation)	`10.0.26100.0 – < 10.0.26100.33296`	`10.0.26100.33296`

Vendors and products

Affected operating systems

Affected operating systems

Windows	microsoft	windows_10_1607	—
Windows	microsoft	windows_10_1809	—
Windows	microsoft	windows_10_21h2	—
Windows	microsoft	windows_10_22h2	—
Windows	microsoft	windows_11_23h2	—
Windows	microsoft	windows_11_24h2	—
Windows	microsoft	windows_11_25h2	—
Windows	microsoft	windows_11_26h1	—
Windows	microsoft	windows_server_2012	`r2`
Windows	microsoft	windows_server_2012	—
Windows	microsoft	windows_server_2016	—
Windows	microsoft	windows_server_2019	—
Windows	microsoft	windows_server_2022	—
Windows	microsoft	windows_server_2025	—

Weakness classes (CWE)

CWE-416Use After Free
Variant
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
Entry at MITRE CWE-416

Public exploit references

Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

Public exploit references

CISA KEV Catalog	CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov	actively exploited	11.08.2026
PoC-in-GitHub (nomi-sec)	CVE-2026-68820_Mass_Exploit (opens in a new tab)github.com	PoC (publicly reported)reported, not verified	26.08.2026
PoC-in-GitHub (nomi-sec)	CVE-2026-68820-Mitigation-PoC- (opens in a new tab)github.com	PoC (publicly reported)reported, not verified	24.08.2026
PoC-in-GitHub (nomi-sec)	Windows-WinSock-UAF-Mitigation (opens in a new tab)github.com	PoC (publicly reported)reported, not verified	15.08.2026
PoC-in-GitHub (nomi-sec)	CVE-2026-68820 (opens in a new tab)github.com	PoC (publicly reported)reported, not verified	13.08.2026

References & sources

Microsoft Security Update GuideWindows Ancillary Function Driver for WinSock Elevation of Privilege VulnerabilityVendor advisory, Patch, Patch, Vendor advisory
cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-68820government-resource, US government resource
pwn.watchpwn.watch: Microsoft Windows Ancillary Function Driver for WinSock : Microsoft Windows Ancillary Function Driver for WinSock Use-After-Free Vulnerabilitypwn-watch
portal.msrc.microsoft.comMicrosoft Windows Ancillary Function Driver for WinSock — CVE-2026-68820pwn-watch
NVD (NIST)NVD: CVE-2026-68820pwn-watch
cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
JPCERT/CCJPCERT/CC JPCERT-AT-2026-0022: Microsoft Releases August 2026 Security Updatesjpcert

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

16.08.2026Record modifiedMicrosoft

1 individual change: Affected versions (publisher)

Show the original change

Individual changes of this event as published by NVD
Type	Action	Before	After
Affected versions (publisher)	changed	Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 21H2 (+17)	Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 21H2 (+17)

Source identifier: secure@microsoft.com

11.08.2026Record modifiedMicrosoft

1 individual change: Affected versions (publisher)

Show the original change

Individual changes of this event as published by NVD
Type	Action	Before	After
Affected versions (publisher)	changed	Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 21H2 (+17)	Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 21H2 (+17)

Source identifier: secure@microsoft.com

11.08.2026CISA KEV entry updated9119a7d8…
4 individual changes: Date Added, Due Date, Required Action, Vulnerability Name
Show 4 original changes
Individual changes of this event as published by NVD
Type Action Before After
Date Added added
—
2026-08-11
Due Date added
—
2026-08-11
Required Action added
—
2026-08-11
Vulnerability Name added
—
2026-08-11
Source identifier: 9119a7d8-5eab-497f-8521-727c672e3725

Individual changes of this event as published by NVD
Type	Action	Before	After
Date Added	added	—	2026-08-11
Due Date	added	—	2026-08-11
Required Action	added	—	2026-08-11
Vulnerability Name	added	—	2026-08-11

11.08.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: active, automatable: no

New references:

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-68820

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-68820
SSVC assessment	added	—	{"id":"CVE-2026-68820","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-11T19:40:14.631211Z"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

11.08.2026ReceivedMicrosoft

CVSS V3.1: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness type: CWE-416

Description added or changed

New references:

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-68820

Show 5 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Affected versions (publisher)	added	—	Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 21H2 (+17)
Description	added	—	Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
CVSS	added	—	AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness type (CWE)	added	—	CWE-416
Reference	added	—	https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-68820

Source identifier: secure@microsoft.com

One NVD translation into another language is hidden.

Linked advisories

@RISK®: The Consensus Security Vulnerability Alert: Vol. 26, Num. 32SANS @RISK20.08.2026
@RISK®: The Consensus Security Vulnerability Alert: Vol. 26, Num. 31SANS @RISK13.08.2026
Patch Actively Exploited Flaws in SharePoint and WinsockSANS NewsBites11.08.2026
Microsoft Patch Tuesday, August 2026SANS NewsBites11.08.2026

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What is affected, what to do

Metrics

Response and mitigation

Prioritisation rationale

Immediate response (0-24 h)

Mitigation layers

Detection rules

Detection rules

Classification under NIS2 and CRA

Description

Affected products

Vendors and products

Affected operating systems

Weakness classes (CWE)

Public exploit references

References & sources

Changes to this CVE

Linked advisories