Fireshare facilitates self-hosted media and link sharing. Prior to version 1.5.3, the fix for CVE-2026-33645 was applied to the authenticated /api/uploadChunked endpoint but was not applied to the unauthenticated /api/uploadChunked/public endpoint in the same file (app/server/fireshare/api.py). An unauthenticated attacker can exploit the checkSum parameter to write arbitrary files with attacker-controlled content to any writable path on the server filesystem. This issue has been patched in version 1.5.3.
https://github.com/ShaneIsrael/fireshare/security/advisories/GHSA-fvvp-rj8g-c7gc
https://github.com/ShaneIsrael/fireshare/releases/tag/v1.5.3
https://github.com/ShaneIsrael/fireshare/pull/520
https://github.com/ShaneIsrael/fireshare/commit/b76915607924756e6fa1a5f6c8823c38d611fb24