Microsoft’s August 2026 Patch Tuesday release addresses more than 421 vulnerabilities across Windows and other Microsoft products. According to BleepingComputer’s analysis, Microsoft has patched three zero-day vulnerabilities this month. One was actively exploited in the wild, while the other two had been publicly disclosed before Microsoft released patches.
The three zero-days include:
- CVE-2026-68820 – Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
- CVE-2026-62832 – Windows User Profile Service Elevation of Privilege Vulnerability
- CVE-2026-72971 – Windows Container Isolation FS Filter Driver (unionfs.sys) Tampering Vulnerability
In addition to the zero-day fixes, Microsoft’s August security release also addresses a large number of Critical-rated vulnerabilities, affecting components and services such as Windows NTFS, DHCP Server, Hyper-V, and the Windows Kernel.
For Windows users, Microsoft has released KB5121003 for Windows 11 versions 24H2 and 25H2, while eligible Windows 10 systems enrolled in the Extended Security Updates (ESU) program receive KB5120249.
August 2026 Patch Tuesday Includes Three Zero-Days
The biggest highlight of Microsoft’s August 2026 Patch Tuesday release is the patch for three zero-day vulnerabilities. One was actively exploited in the wild, while the other two were publicly disclosed before Microsoft released fixes.
A zero-day vulnerability is a security flaw in software that is unknown to the vendor (such as Microsoft) when it is exploited by attackers. Because there’s no patch available when the flaw is discovered, it’s called a “zero-day,” meaning the vendor has zero days to fix it before it’s used in attacks.
The first vulnerability, CVE-2026-68820, affects the Windows Ancillary Function Driver for WinSock (afd.sys) and is an elevation-of-privilege flaw. It is actively exploited in the wild and could allow a local attacker to gain SYSTEM-level privileges on an affected Windows device.
Microsoft also patched CVE-2026-62832, which affects the Windows User Profile Service and could allow an authenticated attacker to gain elevated privileges. The vulnerability was publicly disclosed before Microsoft released the patch, and Microsoft believes exploitation is likely.
The third vulnerability, CVE-2026-72971, affects the Windows Container Isolation FS Filter Driver (unionfs.sys) and is classified as a tampering vulnerability. It was also publicly disclosed before the security update, although Microsoft currently considers exploitation unlikely.
Among the three, CVE-2026-68820 is the most urgent because it has already been exploited. Windows users should install the August 2026 cumulative update to protect their systems against all three vulnerabilities.
Critical Vulnerabilities Also Fixed
In addition to the three zero-day vulnerabilities, Microsoft’s August 2026 Patch Tuesday release fixes 42 vulnerabilities rated Critical, the highest severity rating assigned by Microsoft.
Among the Critical vulnerabilities patched this month, CVE-2026-62878 affecting Windows DNS Server deserves particular attention.
The vulnerability has a CVSS score of 9.8 and is a remote code execution flaw. An unauthenticated attacker could potentially send specially crafted network traffic to an affected DNS server and execute code remotely.
Other notable Critical vulnerabilities affect components including Windows Deployment Services, Microsoft QUIC and Microsoft HPC Pack.
For organizations, these server-side vulnerabilities can be more serious than many of the local privilege-escalation bugs because vulnerable services may be exposed to network-based attacks.
What’s New for Windows 11 Users?
Windows 11 receives its regular cumulative Patch Tuesday updates as part of the August release.
For Windows 11 25H2 and 24H2, Microsoft has released KB5121003. The update moves systems to:
- Windows 11 25H2 — Build 26200.9168
- Windows 11 24H2 — Build 26100.9168
These are the final build numbers listed by Microsoft for the August 11 release.
Along with the security fixes, KB5121003 includes several smaller improvements and reliability fixes.
What’s New in Windows 11 KB5121003
The August update brings the following changes to Windows 11:
- Better File Explorer file sizes: File Explorer can display file sizes using more appropriate units such as KB, MB and GB instead of showing large files only in KB.
- Improved File Explorer tabs: Middle-clicking a folder from the Address Bar or Home page can open it in a new tab.
- Voice Access improvements: Voice Access adds Voice Isolation, which can reduce interference from other speakers and background noise. Korean language support is also included.
- External fingerprint support: Windows Hello Enhanced Sign-in Security can now work with supported external fingerprint readers, expanding the feature beyond PCs with built-in fingerprint sensors.
- Better touchpad controls: Windows 11 adds more control over scrolling and zoom gestures, including accelerated scrolling.
- Improved Windows Search: Search is better at handling typos, incomplete application names and extra characters when looking for apps.
- More system reliability fixes: Microsoft has also addressed issues involving the Taskbar, Start menu, networking, power management and other Windows components.
Microsoft is also continuing its Secure Boot certificate rollout with the August update. The company says additional device-targeting data is being used to expand automatic delivery of the newer certificates to eligible systems.
What’s New for Windows 10 Users?
Windows 10 receives KB5120249 as part of Microsoft’s Extended Security Updates program.
The update applies to supported Windows 10 22H2 and 21H2 systems enrolled in ESU, as well as supported Enterprise LTSC editions.
After installation, the builds become:
- Windows 10 22H2 — Build 19045.7663
- Windows 10 21H2 — Build 19044.7663
Microsoft’s official documentation confirms KB5120249 is the August 11 security update for these supported Windows 10 editions.
What’s New in Windows 10 KB5120249
The Windows 10 update is much smaller in terms of visible changes, but it includes important security and reliability work:
- File History fix: Microsoft fixes an issue where automatic File History backups to an SMB network share could fail with an incorrect “invalid credentials” error.
- More Secure Boot certificate coverage: The update expands Microsoft’s targeting data so more eligible PCs can automatically receive the newer Secure Boot certificates.
- Security fixes: KB5120249 includes the August 2026 security fixes for supported Windows 10 systems.
- Monthly cumulative improvements: The package also carries forward fixes and quality improvements from previous Windows 10 security updates.
- Enterprise and LTSC support: Supported Windows 10 Enterprise LTSC 2021 and IoT Enterprise LTSC 2021 systems also receive the corresponding August security update.
- No new major Windows 10 features: Unlike Windows 11, this month’s Windows 10 release is primarily focused on security, reliability and continued support for eligible systems.
- Secure Boot rollout continues: Microsoft says the newer certificates will continue rolling out through Windows Update over the coming months.
Windows 10 users should remember that regular support for most editions ended in October 2025. The August update is therefore primarily relevant to systems covered by Microsoft’s ESU program or supported LTSC editions.
Should You Install the August 2026 Patch Tuesday Updates?
Yes. The August updates should be installed as soon as practical.
The sheer number of vulnerabilities makes this a significant Patch Tuesday, but the actively exploited CVE-2026-68820 is the biggest reason not to delay.
The Windows DNS Server vulnerability is also particularly concerning for organizations because of its 9.8 CVSS score and remote code execution potential. Publicly disclosed vulnerabilities add another reason to keep systems patched.
How to Install the August 2026 Patch Tuesday Updates
Microsoft is rolling out the August 2026 Patch Tuesday updates through Windows Update for supported Windows devices.
- Windows Update: Go to Settings > Update & Security > Windows Update (or equivalent in older Windows versions) and check for updates.
- WSUS/SCCM: Organizations using Windows Server Update Services (WSUS) or System Center Configuration Manager (SCCM) can deploy updates through their centralized management systems.
- Microsoft Update Catalog: For specific updates or offline installations, you can download them directly from the Microsoft Update Catalog website.
If you prefer to install updates manually, you can download the latest cumulative updates from the Microsoft Update Catalog:
- Windows 11 KB5121003 (Version 25H2/24H2) offline installer Direct Download Link 64-bit.
- Windows 11 KB5120240 (Version 23H2) offline installer Direct Download Link 64-bit.
- Windows 10 KB5120249 (For versions 22H2 and 21H1) Direct Download Links: 64-bit and 32-bit (x86).
Important note:
- Focus on installing critical updates first, as they address the most severe vulnerabilities.
- Enable automatic updates to ensure that security patches are installed promptly.
- Before deploying updates to production systems, it’s recommended to test them in a non-production environment to identify any potential compatibility issues.
- Regularly check the Microsoft Security Update Guide for detailed information about released updates.
Frequently Asked Questions
Patch Tuesday is Microsoft’s monthly security update release, typically published on the second Tuesday of each month. It delivers security patches, bug fixes, and reliability improvements for Windows and other Microsoft products.
Microsoft’s August 2026 Patch Tuesday addresses 421 security vulnerabilities, including Critical vulnerabilities and three zero-day vulnerabilities, two of which were actively exploited before patches became available.
Because it actively exploits zero-days and Critical vulnerabilities, several of which allow remote code execution (RCE). Unpatched systems are at higher risk of compromise, especially if they’re exposed to the internet.
Yes. Microsoft recommends installing the updates because they contain important security fixes, including patches for publicly disclosed vulnerabilities and critical security flaws that could affect Windows devices.
For Windows 11, install KB5121003 and KB5120240. For Windows 10 (ESU), install KB5120249. These cumulative updates include all August 2026 security fixes, as well as stability and reliability improvements.
Go to Settings > Update & Security > Windows Update and click Check for updates. Organizations can use WSUS/SCCM or download offline installers from the Microsoft Update Catalog.
