Remote Desktop: An authentication error has occurred. The function requested is not supported. This could be due to CredSSP encryption oracle remediation
The RDP client and server disagree on CredSSP security updates — one side is patched and enforcing, the other isn’t.
Seen on:
Windows
Meaning
After the CVE-2018-0886 updates, patched clients refuse to connect to unpatched servers (and vice versa depending on policy). The real fix is updating the server; a temporary client policy can relax it.
Common causes
- Server missing CredSSP security updates
- Client policy set to Force Updated Clients
- NLA/CredSSP misconfiguration
⚡ Quick fix
- Install current Windows updates on the server
- Temporarily set Encryption Oracle Remediation to Vulnerable on the client (then revert)
- Use the console/Hyper-V/Azure serial console to patch the server
Detailed fix by platform
Windows
reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters /v AllowEncryptionOracle /t REG_DWORD /d 2 /f # temporary; revert after patching
How to diagnose
- Patches — Server patch level
- Policy — Encryption Oracle Remediation setting on both sides
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Last updated 7 Oct 2026