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.
CredSSP encryption oracle remediationAn authentication error has occurred. The function requested is not supportedThis could be due to CredSSP encryption oracle remediation 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 15 Oct 2026