Fails to run server actions if X-Forwarded-Host header doesn't contain a port

### Link to the code that reproduces this issue https://github.com/nanto/nextjs-nginx-proxy-example ### To Reproduce 1. Run `docker compose up`. 2. Open <http://localhost:3333/>. 3. Click the “Increment” button. ### Current vs. Expected behavior Expected behavior: the “Count: 0” becomes to “Count: 1”. Actual behavior: `Invalid Server Actions request` error happens in client side and the following error message is shown in server side: ``` `x-forwarded-host` header with value `localhost` does not match `origin` header with value `localhost:3333` from a forwarded Server Actions request. Aborting the action. ``` ### Provide environment information ```bash Operating System: Platform: linux Arch: x64 Version: #1 SMP PREEMPT_DYNAMIC Debian 6.1.128-1 (2025-02-07) Available memory (MB): 15976 Available CPU cores: 2 Binaries: Node: 18.20.7 npm: 10.8.2 Yarn: N/A pnpm: 9.6.0 Relevant Packages: next: 15.2.3 // Latest available version is detected (15.2.3). eslint-config-next: N/A react: 19.0.0 react-dom: 19.0.0 typescript: N/A Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) Server Actions ### Which stage(s) are affected? (Select all that apply) next dev (local) ### Additional context Some reverse proxies are configured as `X-Forwarded-Host` header doesn't contain the original port but `X-Forwarded-Port` header contains it. For example, when [nginx-proxy](https://github.com/nginx-proxy/nginx-proxy) with default settings accepts an HTTP request for `https://local.example.com:3333/`, it adds `X-Forwarded-Host: local.example.com`, `X-Forwarded-Port: 3333`, and `X-Forwarded-Proto: https` headers. Current Next.js CSRF prevention logic can't handle such a case and refuse execution of server actions.