Microsoft Windows Ancillary Function Driver for WinSock: memory corruption flaw under attack

What is affected

Microsoft Windows Ancillary Function Driver for WinSock is found on ordinary personal computers and phones, so this is not only a problem for companies. If you use it and have not updated since the fix was released, you are exposed.

Microsoft Windows Ancillary Function Driver for WinSock contains a use-after-free vulnerability that allows an authorized attacker to elevate privileges locally.

What an attacker can do

This is a memory corruption flaw. It lets an attacker corrupt the program's memory by feeding it specially crafted content: a web page, a file or a network message. The result ranges from a crash to the attacker running their own code.

How it is reached

Needs access to the device or a file opened on it

Access the attacker needs

A basic user account

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. Update Microsoft Windows Ancillary Function Driver for WinSock now. Open the update or "About" screen, install whatever is offered and restart the app or device, because the fix is not active until you do.
2. Turn on automatic updates so the next fix arrives without you having to look for it.
3. If your device is too old to receive this update, stop using the affected app for anything sensitive and plan a replacement.

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Vendor advisories and fixes

• portal.msrc.microsoft.comportal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-68820

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on August 11, 2026, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by August 25, 2026, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 0.3% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 24% of all scored vulnerabilities.

Its CVSS severity score is 7.0 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

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