Affected: Homebrew: mailcatcher

## Summary

`Rack::Static` normalizes the request path with `Utils.clean_path_info` when deciding which file to serve, but matches `header_rules` against a path that is only URL-decoded. A request containing dot segments, raw or percent-encoded, is served the normalized target file while the header rules for that file's location are not applied.

This allows an attacker to receive a protected static file without the security headers configured for it.

## Details

`Rack::Static#call` computes the served path as `Utils.clean_path_info(Utils.unescape_path(path))`. `Rack::Static#applicable_rules` applies only `Utils.unescape_path` before testing string and regular expression rules. A request for `/assets/../uploads/file.html` or `/assets/..%2fuploads/file.html` is served as `uploads/file.html`, but the decoded path `/assets/../uploads/file.html` does not start with `uploads`, so a rule scoped to that directory never matches.

The fix for CVE-2026-34786 (GHSA-q4qf-9j86-f5mh) added URL decoding to rule matching but did not add dot segment normalization, so versions that include that fix remain affected.

## Impact

Applications that use `Rack::Static` `header_rules` to attach security-relevant headers to particular paths or file types are affected. An unauthenticated attacker who knows the path of a protected file can request it through a dot segment path and receive it without those headers, for example without `Content-Disposition: attachment` or a restrictive `Content-Security…

Affected: rack

Rack is a modular Ruby web server interface. Prior to 2.2.25, 3.1.23, and 3.2.8, Rack::Static serves a path after Utils.clean_path_info normalization but evaluates header_rules against a path that is only URL-decoded. An unauthenticated attacker can request a known file through raw or percent-encoded dot segments and receive it without path-specific security headers such as Content-Disposition or Content-Security-Policy. Applications that do not use path-specific header_rules are not affected. This issue is fixed in versions 2.2.25, 3.1.23, and 3.2.8.