Microsoft fixes bug behind Windows 10 Connected Cache delivery issues

Microsoft has fixed a known Windows 10 update issue that broke Microsoft Connected Cache (MCC) node discovery on enterprise networks.

The fix is included with the KB5040525 July 2024 preview update for Windows 10 22H2 released yesterday, which also comes with fixes for WDAC issues causing memory leaks and app failures,

"This issue was resolved by Windows updates released July 23, 2024 (KB5040525), and later," Microsoft said in a Windows health dashboard update on Tuesday. "We recommend you install the latest security update for your device. It contains important improvements and issue resolutions, including this one."

MCC servers are software-only caching solutions that can be deployed on Windows servers, bare-metal servers, or VMs and used to cache and deliver content downloaded from Microsoft's content delivery network (CDN). For example, after a client downloads a Windows update, other users on the same enterprise network can be directed to one of the MCC nodes for quicker delivery over the local network.

As the company explains, this bug only affects Windows 10 21H2 and 22H2 devices configured to find MCC endpoints using DHCP Option 235. Home users are unlikely to be impacted because Connected Cache configured via DHCP Option 235 is only commonly used in enterprise environments.

"After installing the January 2024 non-security update (KB5034203), released January 23, 2024, or later updates, some Windows devices which use the DHCP Option 235 for discovery of Microsoft Connected Cache (MCC) nodes in their network might be unable to use the MCC nodes," Microsoft said when it first confirmed the issue in April.

"Instead, these Windows devices will download updates and apps from the public internet and IT administrators would see increased download traffic on their internet routes."

Workarounds available

For those who don't want to install the KB5040525 monthly optional cumulative update, Microsoft provides temporary workarounds that enable Windows admins to revive download caching for end-users.

Option one involves setting up the Microsoft Connected Cache endpoint in the DOCacheHost policy using instructions on the Cache hostname page.

Additionally, you can set DOCacheHostSource to 1 or remove it, as described in the Cache hostname source support document.

Affected admins can also address the issue using Group Policies, which can be accessed through Redmond's support channel (they can also request assistance through the paid Microsoft Support for Business channel).

On Tuesday, Microsoft warned customers that some Windows 10, Windows 11, and Windows Server devices will get sent into BitLocker recovery after installing the July 2024 Windows security updates.

Those impacted are prompted to enter their BitLocker recovery key to unlock the drive, allowing the system to boot normally from the BitLocker recovery screen.