SSO doesnt work with Chrome and Edge

Technical assistance
1
  • Used Zammad version: 6.5.0-1750744147.bf43fc31.bookworm
  • Used Zammad installation type: package
  • Operating system: Debian
  • Browser + version: Chrome Version 138.0.7204.97

Expected behavior:

  • Did SSO via Kerberos exactly like in the SSO manual. It works on Firefox but it doesnt work on Chrome or Edge.

What I tried:

  • The FQDN of Zammad is set in the AuthServerWhitelist policy
  • Added Zammad FQDN in Internet Options under Security > Local Intranet > Sites > Advanced.
  • Selected “Require server verification (https:) for all sites in this zone”.
  • Selected Under Security level for this zone > Custom level… > Settings > User Authentication > Logon, “Automatic logon only in Intranet Zone”.
  • Tested Users are in the active AD and the zammad host is treated as a local intranet server
  • Checked the Chrome Dev tools with the SSO error: 401 Unauthorized
  • On Chrome in the Request header the Auth isnt there
  • In Firefox the Auth request is in the header
  • Double checked the Whitelist settings for Chrome
  • Removed all cookies in Chrome and restarted it
  • In the Linux appache error log following error occurs: GSS ERROR In Negotiate Auth: gss_accept_sec_context() failed: [An unsupported mechanism was requested (Unknown error)]
  • Checked the AES265 box is selected in the Kerberos account

Steps to reproduce the behavior:

  • Firefox works always, chrome and edge never

Thanks for the Help, what else can I try?