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Intranet site 401 Unauthorized kerberos SSO

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Rasmus Geisor
Rasmus Geisor

Hi!

We have a intranet site that works in Edge and Chrome without issues with the site added to "internet options". But for some reason we are getting 401 Unauthorized when trying to access it from Firefox. I have tried adding the urls to: network.automatic-ntlm-auth.trusted-uris network.automatic-ntlm-auth.allow-proxies: true network.automatic-ntlm-auth.allow-non-fqdn: true network.auth.force-generic-ntlm: false network.auth.force-generic-ntlm-v1: false

Ingocnito mode , same error. I have tried disabling all plugins. Disabled DNS over HTTPS.

HTTP/1.1 401 Unauthorized Server: Microsoft-IIS/10.0 WWW-Authenticate: Negotiate X-Powered-By: ASP.NET Date: Mon, 25 May 2026 08:15:41 GMT Content-Length: 0

Regards Rasmus

Hi! We have a intranet site that works in Edge and Chrome without issues with the site added to "internet options". But for some reason we are getting 401 Unauthorized when trying to access it from Firefox. I have tried adding the urls to: network.automatic-ntlm-auth.trusted-uris network.automatic-ntlm-auth.allow-proxies: true network.automatic-ntlm-auth.allow-non-fqdn: true network.auth.force-generic-ntlm: false network.auth.force-generic-ntlm-v1: false Ingocnito mode , same error. I have tried disabling all plugins. Disabled DNS over HTTPS. HTTP/1.1 401 Unauthorized Server: Microsoft-IIS/10.0 WWW-Authenticate: Negotiate X-Powered-By: ASP.NET Date: Mon, 25 May 2026 08:15:41 GMT Content-Length: 0 Regards Rasmus

All Replies (3)

jbr
jbr
  • Top 25 Contributor

I assume it's configured with network.negotiate-auth.trusted-uris and related network.negotiate-auth.delegation-uris — according to https://firefox-admin-docs.mozilla.org/reference/policies/authentication/ where it's configured in most cases.

Linux specifics aside, the Firefox config steps are also described e.g. in https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/5/html/deployment_guide/sso-config-firefox

Rasmus Geisor
Rasmus Geisor Umnini wombuzo

Hi!

Yes these are all tested except network.auth.private-browsing-sso, but this one did not help either. These settings are only changed in the about:config at first. Will deploy them later to everyone when we find the issue.

Regards Rasmus

jbr
jbr
  • Top 25 Contributor

Do you have any logs from the server side, Rasmus? — To see if there are actually any attempts to submit the kerberos ticket at all? Or it's a just a single 401 only… and then silence.

Also please share your setup (OS versions, browser distribution/channel etc.?) — it's not apparent what versions you're trying to deploy as this question was not submitted from within one.

Buza umbuzo

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