Problem in Parsing JWT token.

Question

Problem in Parsing JWT token.

Abhishek 20

I have an API service webapp. The JWT token used for authorization has 13 claims. The main deployed web app parses all the claims correctly. I deployed a test version of this webapp without any changes in the jwt auth module. Now 3 claims are not being parsed in this version. There is no change in the jwt auth module between the two versions.

What can cause this difference between the two ?

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Answer 1

Hi @Abhishek ,

You can try the following steps to identify what’s causing the difference in parsed claims between your deployed and test versions. These are some common areas where differences usually appear, even when the JWT authentication module itself hasn’t changed

Different token source Check if the test environment is receiving the same JWT as production. In some cases, the identity provider or token issuer for the test app issues a slightly different token (for example, fewer claims or a different scope).
Configuration differences Even small differences in appsettings.json or environment variables (such as issuer, audience, or TokenValidationParameters) can affect which claims are recognized or filtered out.
Claim mapping behavior ASP.NET automatically maps certain claim types (like sub → nameidentifier). If one environment clears the default claim type map (JwtSecurityTokenHandler.DefaultInboundClaimTypeMap.Clear()) and the other doesn’t, the claims collection may look different.
Middleware order or missing components Make sure the test deployment has the same middleware setup — for example, UseAuthentication() and UseAuthorization() should appear in the same order as production. If a custom middleware modifies claims, verify it’s included in both versions.
Build or dependency differences Sometimes the build or NuGet package versions differ slightly between environments, especially if one is rebuilt with newer dependencies.

To narrow it down:

Decode both JWTs using jwt.io and confirm whether the missing claims are actually present in the token.
Log or inspect User.Claims right after authentication in both environments.
Compare the full authentication configuration and middleware order between the two deployments.

Even if the code looks identical, environmental or configuration differences are usually the cause of this kind of behavior.

If you find any discrepancies or still see missing claims after checking these areas, please share the relevant configuration snippet or token payload (without sensitive data) so I can help you look deeper into it.

Abhishek 20 Reputation points

2025-10-24T17:37:35.2466667+00:00

Many thanks for the reply Danny,

Troubleshooting & Approaches we tried

Reviewed Token Handler / Middleware (Program.cs): Cleared and rechecked the token handling pipeline and middleware configuration. * No configuration differences found that could directly cause claim loss.

Renamed Claim Keys: Updated claim names (e.g., from Name → user_name) to avoid potential conflicts with reserved claim types. The issue persisted — renamed claims still not extracted.

(JwtSecurityTokenHandler.DefaultInboundClaimTypeMap.Clear()) was also used.

Manual JSON Extraction: Extracted the JWT payload manually and parsed it as JSON. All expected claims were successfully retrieved, confirming that token data is intact.

Presently this workaround is working but don't think that this is the right approach.
Danny Nguyen (WICLOUD CORPORATION) 3,500 Reputation points Microsoft External Staff

2025-10-27T10:53:28.0633333+00:00

Thanks for the detailed follow-up — that helps narrow it down quite a bit.

Since manual JSON parsing shows all claims are present, the issue is happening after token validation, during claim mapping or identity construction.

You can check these areas next:

Ensure claim mapping is fully disabled

Even if you’ve called JwtSecurityTokenHandler.DefaultInboundClaimTypeMap.Clear(), that might not apply to the handler instance used by the JWT middleware.

Try this inside your AddJwtBearer setup:

options.SecurityTokenValidators.Clear(); options.SecurityTokenValidators.Add(new JwtSecurityTokenHandler { InboundClaimTypeMap = new Dictionary<string, string>() });

This guarantees no automatic claim type remapping occurs.

Check TokenValidationParameters settings

Look for any values like NameClaimType or RoleClaimType that could cause the framework to treat some claims specially and hide duplicates.

Review custom claim transformations

If there’s an IClaimsTransformation service or any middleware that adjusts claims, confirm it’s identical between environments — those often remove or rename claims unexpectedly.

Since the token itself is correct, the difference is probably in how the validated ClaimsPrincipal is being built.

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Problem in Parsing JWT token.

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