This affects the package cesanta/mongoose before 7.6. The unsafe handling of file names during upload using mg_http_upload() method may enable attackers to write files to arbitrary locations outside the designated target folder.
https://snyk.io/vuln/SNYK-UNMANAGED-CESANTAMONGOOSE-2404180
https://github.com/cesanta/mongoose/commit/c65c8fdaaa257e0487ab0aaae9e8f6b439335945