CVE-2026-25539: b3log Siyuan

High severity, CVSS 7.2. EPSS: 1.1% chance of exploitation in the next 30 days.

SiYuan is a personal knowledge management system. Prior to version 3.5.5, the /api/file/copyFile endpoint does not validate the dest parameter, allowing authenticated users to write files to arbitrary locations on the filesystem. This can lead to Remote Code Execution (RCE) by writing to sensitive locations such as cron jobs, SSH authorized_keys, or shell configuration files. This issue has been patched in version 3.5.5.

Affected products

• b3log Siyuan: up to and including 3.5.3

Published 2026-02-04. Last modified 2026-06-17.