Networking issues after October 2026 Windows update

The upcoming October 2026 Windows security update has raised concerns among system administrators and businesses still using NTLMv1, an outdated authentication protocol. This seemingly minor change could have significant repercussions on network connectivity for those who have not transitioned to more modern technologies.

Prior to this update, Windows allowed NTLMv1-derived credentials for Single Sign-On (SSO), albeit with warnings regarding their use. However, with the new update, requests attempting to use these credentials will be blocked by default, potentially impacting connections via Wi-Fi, Ethernet, and VPN.

## Why it matters This change is crucial as many businesses still rely on NTLMv1 for compatibility with legacy systems. Blocking this protocol could disrupt daily operations and create access issues to critical resources, forcing many organizations to accelerate their migration to more secure solutions.

## What we know The update does not automatically set the BlockNtlmSSO registry value, meaning administrators must manually configure it to avoid blocking. Setting it to 0 will temporarily allow NTLMv1 usage, but this is only a short-term fix that does not address the underlying issue of reliance on obsolete technologies.

## What remains unclear It is still unconfirmed how many users or businesses will be affected by this change, nor what the long-term impact on the security of networks relying on NTLMv1 will be. Information on Microsoft's recommendations for those still dependent on this protocol is also lacking.