Affected: rack, Red Hat Satellite 6

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static determines whether a request should be served as a static file using a simple string prefix check. When configured with URL prefixes such as "/css", it matches any request path that begins with that string, including unrelated paths such as "/css-config.env" or "/css-backup.sql". As a result, files under the static root whose names merely share the configured prefix may be served unintentionally, leading to information disclosure. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

Affected: RubyGems: rack

## Summary

`Rack::Static` determines whether a request should be served as a static file using a simple string prefix check. When configured with URL prefixes such as `"/css"`, it matches any request path that begins with that string, including unrelated paths such as `"/css-config.env"` or `"/css-backup.sql"`.

As a result, files under the static root whose names merely share the configured prefix may be served unintentionally, leading to information disclosure.

## Details

`Rack::Static#route_file` performs static-route matching using logic equivalent to:

```ruby @urls.any? { |url| path.index(url) == 0 } ```

This checks only whether the request path starts with the configured prefix string. It does not require a path segment boundary after the prefix.

For example, with:

```ruby use Rack::Static, urls: ["/css", "/js"], root: "public" ```

the following path is matched as intended:

```text /css/style.css ```

but these paths are also matched:

```text /css-config.env /css-backup.sql /csssecrets.yml ```

If such files exist under the configured static root, Rack forwards the request to the file server and serves them as static content.

This means a configuration intended to expose only directory trees such as `/css/...` and `/js/...` may also expose sibling files whose names begin with those same strings.

## Impact

An attacker can request files under the configured static root whose names share a configured URL prefix and obtain their contents.

In affected deployme…