WebDyne versions from 3.007 before 3.022 for Perl execute .psp files outside the document root via path traversal in the PSGI API route fallback

WebDyne versions from 3.007 before 3.022 for Perl execute .psp files outside the document root via path traversal in the PSGI API route fallback.

When a request matches no file, the PSGI handler retries it as an API route through api_filename. That keeps .. segments in the request path and only checks that the joined path starts with the document root, which a request for /../private passes.

A remote attacker can run the embedded Perl in any .psp file the server can read, such as one uploaded to a directory outside the document root.