I'm trying to gauge whether it's safe to install the latest monthly updates on production domain controllers. There's been some discussion about known issues, but I haven't seen a clear summary of what is actually affected. Has anyone deployed them yet, and have you encountered problems? Environments with fewer than 1,000 servers are welcome to share their experience too.
4 Answers
The main concern with the recent domain controller updates is the enforcement of RC4 deprecation. If accounts, trusts, or services still depend on RC4 or DES instead of AES Kerberos encryption, authentication problems are possible. Audit the environment before deploying broadly.
We held the updates back on a few domain controllers while investigating RC4 traffic. A couple of secondary controllers were patched first and have been stable so far. Other environments running Server 2019, 2022, and 2025 also reported no significant issues, though one update-reporting problem was resolved with a Microsoft-provided script.
For production, I’d use a staged rollout: patch a small set of secondary controllers, monitor authentication and replication, then expand gradually. Several large environments reported no issues with the July updates, but postponing deployment is reasonable if RC4 dependencies are still showing up.
The updates aren’t available yet—they’re scheduled for tomorrow. It may be better to wait for the release notes and early deployment reports before drawing conclusions.
Thanks, that explains the confusion. I was wondering whether a new critical vulnerability had just dropped, but I probably shouldn’t have started investigating before release day.