Armeria is an open source microservice framework. In affected versions an attacker can access an Armeria server's local file system beyond its restricted directory by sending an HTTP request whose path contains `%2F` (encoded `/`), such as `/files/..%2Fsecrets.txt`, bypassing Armeria's path validation logic. Armeria 1.13.4 or above contains the hardened path validation logic that handles `%2F` properly. This vulnerability can be worked around by inserting a decorator that performs an additional validation on the request path.

Affected: Maven: com.linecorp.armeria:armeria

### Impact

An attacker can access an Armeria server's local file system beyond its restricted directory by sending an HTTP request whose path contains `%2F` (encoded `/`), such as `/files/..%2Fsecrets.txt`, bypassing Armeria's path validation logic.

### Patches

Armeria 1.13.4 or above contains the hardened path validation logic that handles `%2F` properly.

### Workarounds

This vulnerability can be worked around by inserting a decorator that performs an additional validation on the request path, e.g.

```java Server .builder() .serviceUnder( "/files", FileService .of(...) .decorate((delegate, ctx, req) -> { String path = req.headers().path(); if (path.contains("%2f") || path.contains("%2F")) { return HttpResponse.of(HttpStatus.BAD_REQUEST); } return delegate.serve(ctx, req); }) ) .build() ```

### For more information

If you have any questions or comments about this advisory: * Open an issue in [line/armeria](https://github.com/line/armeria) * Chat with us at [Slack](https://armeria.dev/s/slack)

### Credits

This vulnerability was originally reported by Abdallah Zaher ([elcayser-0x0a](https://hackerone.com/elcayser-0x0a?type=user)).