Spring Web request header with diacritic is improperly encoded depending on payload

Affects: Spring Boot 2.6.1 and 2.6.14

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I'm facing a bug that I'm able to reproduce in different projects with Java 11 and Spring Boot 2.6.1 and 2.6.14.

This error happens only when the request contains some diacritic text. Example: firstname: Ève

When the request does not contain a payload, the application receives Ève.

When the request contains a payload, the application receives à ve.

According to my tests the payload content doesn't matter.

This curl command triggers the bug:

curl --location --request POST 'http://localhost:8080/hello' \
--header 'Content-Type: application/json' \
--header 'firstname: Ève' \
--data-raw '{ }'

This curl command does not trigger the bug:

curl --location --request POST 'http://localhost:8080/hello' \
--header 'Content-Type: application/json' \
--header 'firstname: Ève'`

Is it a known issue?

Is it already fixed for last versions?

I've found nothing related to that.

Regards

Comment From: sbrannen

Hi @Guidebom,

Congratulations on submitting your first issue for the Spring Framework! 👍

If you would like for us to assist you, please provide a minimal sample application (or integration test) that demonstrates the issue -- preferably as a public Git repository or ZIP file that we can download and run.

Thanks

Comment From: Guidebom

Hi @sbrannen thanks for the quick answer.

You can find the project here: https://github.com/Guidebom/diacritic-bug/tree/main

Please let me know if you need anything else.

Comment From: rstoyanchev

I'm not able to reproduce the issue. Note that I needed to modify the sample to change the "/hello" method to a POST mapping, and also pass the HttpServletRequest into the controller method. That aside I get the same result with both sample curl requests when I call request.getHeader("firstname").

Moreover, the description is for values that come from the HttpServletRequest and thus not related to anything that Spring MVC does. If you want to confirm that, I suggest using a Filter (i.e. before it gets to Spring MVC) or a plain Servlet.

I'm closing the issue as it is most likely not anything related to Spring MVC but feel free to comment further.