Fix Azure WAF & AD OpenID Connect

When you’re using Azure WAF and Azure Active Directory OpenID Connect, you can experience the WAF blocking on the rule: SQL Comment Sequence Detected.

This is the real solution, please don’t use the solution that Microsoft Azure gives you, it’s very dangerous.

Microsoft Azure – Dangerous way

When you ask the support, they escalate and the only solution that they give you is: you need to disable this rule.

What The Hell!

They want us to disable the rule for the entire WAF so the entire traffic.

It’s easy to see that Microsoft will never change about stupid things and also about their services.

The Right Way: Custom Rule

We just need to allow the traffic on a specific setting: a value at the beginning of a cookie.

It’s not a joke, I use it in production and it works.

The logic:

If: String


  • variable RequestHeaders
  • Header name: Cookie

Operation: is

Operator: Begins with

Transformations: keep empty

Match value: .AspNetCore.OpenIdConnect.

Then: Allow traffic

Screenshot from Azure Portal

azure openid connect - waf custom rule

Never forget

When you need to write and enable custom rules, keep in mind to restrict to required URLs when it’s not affecting all endpoints.