Fireshare 1.5.1 contains an authenticated path‑traversal flaw in its chunked upload endpoint. The checkSum multipart field is concatenated directly into a filesystem path without sanitization, allowing a logged‑in user to write files to arbitrary locations that the Fireshare process can reach, such as /tmp in a container. This can be used to overwrite configuration files, deploy malicious scripts or binaries, and ultimately break the integrity of the deployment. The vulnerability itself does not grant remote code execution directly but it provides a vehicle for follow‑on attacks if attacker code is placed in a web‑executable location.

The affected product is Fireshare by ShaneIsrael, version 1.5.1. All installations running this exact version are vulnerable. The vulnerability was fixed in release 1.5.2; no other versions are listed as affected.

The CVSS score of 7.1 indicates a high severity due to the potential for destructive writes and subsequent exploitation. The EPSS score of less than 1 % suggests that the probability of public exploitation is currently low. The issue is not listed in CISA’s KEV catalog. Because the exploit requires authentication, the attack vector is likely internal or requires an attacker already able to reach the application. If privileged file permissions exist, an attacker who can write to sensitive paths could gain local code execution or other privilege escalation.