Fossil 2.18 on Windows allows attackers to cause a denial of service (daemon crash) via an XSS payload in a ticket. This occurs because the ticket data is stored in a temporary file, and the product does not properly handle the absence of this file after Windows Defender has flagged it as malware.

Fossil before 2.14.2 and 2.15.x before 2.15.2 often skips the hostname check during TLS certificate validation.

Fossil before 2.10.2, 2.11.x before 2.11.2, and 2.12.x before 2.12.1 allows remote authenticated users to execute arbitrary code. An attacker must have check-in privileges on the repository.