The HTTP fallback for SIP connection in Lync must be disabled.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-223345 | SRG-APP-000219 | O365-LY-000002 | SV-223345r1043178_rule | 2026-02-12 | 3 |
Description
Prevents from HTTP being used for SIP connection in case TLS or TCP fail.
ℹ️ Check
Verify the policy value for Computer Configuration >> Administrative Templates >> Skype for Business 2016 >> Microsoft Lync Feature Policies "Disable HTTP fallback for SIP connection" is set to "Enabled".
Use the Windows Registry Editor to navigate to the following key:
HKLM\Software\Policies\Microsoft\office\16.0\lync
If the value disablehttpconnect is REG_DWORD = 1, this is not a finding.
✔️ Fix
Set the policy value for Computer Configuration >> Administrative Templates >> Skype for Business 2016 >> Microsoft Lync Feature Policies "Disable HTTP fallback for SIP connection" to "Enabled".