Yaws 1.91 has a directory traversal vulnerability in the way certain URLs are processed. A remote authenticated user could use this flaw to obtain content of arbitrary local files via specially-crafted URL request.

Yaws 1.91 allows Unauthenticated Remote File Disclosure via HTTP Directory Traversal with /%5C../ to port 8080. NOTE: this CVE is only about use of an initial /%5C sequence to defeat traversal protection mechanisms; the initial /%5C sequence was apparently not discussed in earlier research on this product.