SignatureDoesNotMatch problem when uploading img file using presignedURL

I'm trying to enable users to upload images directly to an S3 bucket via a presigned URL. The flow is as follows: client -> server -> S3 to obtain presigned URL -> server -> client This allows the client to upload the image directly to the bucket using a form submission and the presignedURL. But when getting the presigneURL, this error arises. SignatureDoesNotMatch problem when uploading img file using presignedURL I guess the problem arises when the server is fetching the presignedURL from S3, as it attaches an 'Authorization' header. Our app server also has an app token (for shopping mall user information) that is named 'Authorization', and it seems to overwrite the 'Authorization' for the presignedURL when it's sent to the client. We are injecting the header like using 'Mod header' this when test. We are injecting the header like using 'Mod header' this when test. The reasons why I guess this error is realated to the header. The the behavior works just fine when I turn off the 'Authorization' header of our app. This S3 API Reference says "all Amazon S3 operations use the 'Authorization'request header to provide authentication information" Authorization: AWS4-HMAC-SHA256 Could anyone provide some ideas on how to address this issue? or maybe my guess is wrong?