Severe Internet Throttling After 2026-11 Security Update

Microsoft has not listed Wi‑Fi throughput throttling as a known issue in KB5132061/build 26300.9974, so preserve diagnostic data first and then reinstall the laptop manufacturer’s Killer AX1675x driver.

KB5132061 applies to Windows 11 26H2 and incorporates earlier October updates, but its documented fixes and known issues do not include reduced Internet speed.^1^ The current 26H2 release-health list likewise has no Wi‑Fi throttling entry.^2^

1. Record the wireless link state

Before resetting networking or removing the driver, open Terminal (Admin) and run:

netsh wlan show drivers
netsh wlan show interfaces
netsh wlan show networks mode=bssid
netsh wlan show profiles
netsh wlan show wlanreport

Record:

• Driver version and date.
• Radio type, channel, receive/transmit rate, and signal from show interfaces.
• Whether the connection is using 2.4 GHz, 5 GHz, or 6 GHz.
• The path printed for the generated WLAN report.

Microsoft recommends collecting this baseline before resets or driver removal because those operations can erase evidence or temporarily change the behavior.^3^

Also compare:

• Wi‑Fi versus Ethernet, if available.
• A single large download versus multiple speed-test services.
• The result with any VPN or third-party network/security filtering temporarily disconnected.

If Ethernet reaches normal speed but Wi‑Fi does not, focus on the Killer driver, radio band, and access-point negotiation. Your proximity to the access point establishes strong coverage but does not establish which band or link rate Windows negotiated.

Note the units: 800 Mbps is approximately 100 MB/s, while 3 MB/s is approximately 24 Mbps. That remains a major reduction, but use the same units when comparing tests.

2. Reinstall the OEM Killer Wi‑Fi driver

Microsoft specifically recommends removing and reinstalling the network-adapter driver when connectivity stopped working correctly after a recent update.^4^

1. Download the latest Wi‑Fi driver for the exact laptop model from the laptop manufacturer’s support site. Keep the installer locally before removing anything.
2. Open Device Manager → Network adapters.
3. Right-click Killer(R) Wi‑Fi 6E AX1675x 160MHz Wireless Network Adapter (210NGW).
4. Select Uninstall device.
5. Select Attempt to remove the driver for this device, and then select Uninstall.
6. Restart Windows.
7. Install the downloaded OEM driver, restart again, and repeat the same throughput test.

If the newest OEM driver remains slow and Driver → Roll Back Driver is available in the adapter properties, test the immediately previous OEM driver. Do not substitute a driver intended for a different Killer adapter variant.

3. Reset the Windows network stack only if the driver reinstall fails

Run these commands from Terminal (Admin), in order, and restart afterward:^4^

netsh winsock reset
netsh int ip reset
ipconfig /release
ipconfig /renew
ipconfig /flushdns

Then reconnect and retest on another available frequency band. Microsoft’s Wi‑Fi guidance recommends testing a different band when the router exposes separate networks.^4^

4. Use update removal as a temporary A/B test

If the speed was normal immediately before KB5132061 and remains limited after the driver and stack repairs:

1. Open Settings → Windows Update → Update history.
2. Under Related settings, select Uninstall updates.
3. Select KB5132061, if Windows offers it, and choose Uninstall.
4. Restart and repeat the identical test on the same access point and band.

Some updates cannot be removed. Microsoft also recommends trying an in-place reinstall of the current Windows version before uninstalling a security update.^5^

Removing a security update restores exposure to vulnerabilities addressed by that update, so use this only as a short diagnostic test—not a permanent configuration—and reinstall current security updates afterward.^6^

If uninstalling KB5132061 immediately restores throughput, submit the before/after results, driver details, and WLAN report through Feedback Hub, then use Get Help or Microsoft Support. The 26H2 release-health page identifies those as the consumer support and reporting routes.^2^

References

1. November 10, 2026—KB5132061 (OS Builds 26300.9974, 26200.9974 and 26100.9974) | Microsoft Support
2. Windows 11, version 26H2 known issues and notifications
3. Advanced troubleshooting wireless network connectivity
4. Fix Wi-Fi connection issues in Windows | Microsoft Support
5. [Windows 11](https://support.microsoft.com/windows/deployment/updates-lifecycle/how-to-uninstall-a-windows-update#summary)
6. Understanding the risks: Why you should not uninstall security updates | Microsoft Support