Azure AD authentication query string too long

We are receiving error “AADSTS90015 Requested query string is too long.” today when logging on to our site protected by Cloudflare Access Zero Trust via Azure AD authentication.

We’ve always been using the same origin URL, which is 100 characters long in total. This usually hasn’t been a problem.

Microsoft seem to advise that the POST authentication method should be used when authenticating with Azure AD rather than the redirect method to handle this problem. I couldn’t see a way to enable that in the zero trust console.

Any assistance appreciated.

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We are also having this very same issue, and it started recently too. Seems Cloudflare changed something in their redirect that makes the string long enough to trip this error.