MacOS 26.6.1 breaks VNC.
MacOS 26.6.1 breaks VNC.
This update, just released today, breaks VNC. After installing macos 26.6.1 the machine reboots with Remote Access disabled. I did turn it back on, but then when I tried to use RealVNC, after it takes my VNC password it just spins forever without connecting. This has disabled remote admin for all of our users.
I found the fix with the help of ChatGPT:
Apple changed the Screen Sharing server configuration state during the update, and the default when you re-enable it is now Remote Management. And Remote Management's VNC-password behavior isn't equivalent to standalone Screen Sharing's VNC-password behavior.
The critical distinction in macOS 26.6.1 is apparently now:
Remote Management ≠ Screen Sharing, even though both expose screen-control functionality and historically overlapped heavily.
When 26.6.1 disabled the service and I re-enabled it, MacOS turned on Remote Management, putting the machine into the ARD-managed state. The UI even says this indirectly when you try to access the Screen Sharing control panel:
“This feature is controlled by Remote Management.”
Turning Remote Management OFF and then explicitly enabling Screen Sharing + “VNC viewers may control screen with password” restores the legacy VNC server behavior. Note that these sessions are unencrypted, but if you're remoting in through an SSLVPN service, as I am, then encryption over the Internet is preserved. And the password is not sent in cleartext in regular VNC anyway. Classic RFB VNC Authentication uses a challenge-response mechanism: the server sends a random challenge, and the client encrypts that challenge using a DES-derived key based on the VNC password. The response goes back to the server. The subsequent VNC session, however, is unencrypted.
This scared me, as we have dozens of remote support techs in government environments that have only iPads for remote access to hundreds of systems. They're all protected behind SSLVPN, but to lose support on a weekend like this would be horrific. The 26.6.1 update is rolling out automatically, and I have my work cut out for me fixing the VNC settings, but that's easy to do via a Mac running Screen Sharing, which still works the same.
Alas, the following CLI no longer works since MacOS 12:
kickstart -deactivate
<some command to enable standalone Screen Sharing>
<some command to set VNC password>
Instead you need Apple's full-fledged MDM, and even then it isn't clear that you can turn ON Screen Sharing, only turn it off.