TLS version transition

TLS 1.2 is being deprecated in favor of TLS 1.3. The IETF has not published an exact timeline when TLS 1.2 will be officially sunsetted. RADIUS implementations that offer TLS 1.3 support also support TLS 1.2. Most endpoints detect both versions and may fallback to tLS 1.2 if necessary to complete the handshake. Some RADIUS vendors do not support TLS 1.3 yet. Other vendors released a version of TLS 1.3 that was not fully compliant. This latter scenario will be most problematic for Windows endpoints running Win11 22H2 update.

TLS 1.3 and Windows 11

Beginning with the Win11 22H2 update TLS 1.3 is now prioritized over TLS 1.2 for 802.1x connections. If the endpoint detects TLS 1.3 in the RADIUS handshake, the endpoint will stay with TLS 1.3 until the handshake completes. If only TLS 1.2 is offered, the endpoint will negotiate with TLS 1.2. The issue occurs if RADIUS is running a non-compliant (not fully implemented) version of TLS .1.3. In this scenario the endpoint detects TLS 1.3 and stays with it. This will result in the endpoint failing to connect, as it will not fall back to TLS 1.2. 

Impact Scenarios

✅ Win11 22H2 w/ RADIUS TLS 1.2 Only: Most clients should work

✅ Win11 22H2 w/ RADIUS TLS 1.3 (fully-compliant): Most clients should work

❌ Win11 22H2 w/ RADIUS TLS 1.3 (non fully-compliant): Most clients may fail

Workarounds and Resolution

It is advised that institutions discuss with their Systems and Security teams before implementing any changes.

Day 0 "Quick" Workarounds

RADIUS-Side Workaround (Preferred)

(warning) FreeRADIUS: (Known Impact with Specific Versions)

    • Certain earlier releases of FreeRADIUS have non fully-compliant support for TLS 1.3.
    • In Freeradius 3.2.1 (or older) you can set "tls_max_version = "1.2"".
      • This effectively disables TLS 1.3 negotiation and the endpoint should successfully negotiate via TLS 1.2. 
      • Testing with version 3.2.1-1 has shown this change allows Windows 11 22H2 to auth, and the logs indicate that it's using TLS 1.2
    • The issue appears to be resolved in the latest release of FreeRADIUS (Version 3.2.2 Released 2023.02.16)
    • Prior releases of FreeRADIUS may contain a patch update as well. Check with the vendor for the latest Release Notes

✅ Aruba ClearPass:

    • Current versions of ClearPass do not support TLS 1.3 for RADIUS.
    • Because TLS 1.3 is not present in the handshake negotiation the endpoint should successfully negotiate via TLS 1.2

✅ Microsoft NPS:

✅ Cisco ISE

    • Cisco ISE does not support TLS 1.3

Resolution (Address When You Can)

  • It is likely more client OS's will begin to prioritize TLS 1.3
  • It is likely TLS 1.2 support will be deprecated although exact date is unknown
  • Ensure your RADIUS server is running a fully-compliant release for TLS 1.3 support
  • Check with your specific RADIUS vendor for the latest on TLS 1.3 support
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