CVE-2026-25539 CRITICAL

CVE-2026-25539: SiYuan has Arbitrary File Write via /api/file/copyFile leading to RCE

Vendor Siyuan-Note
Product siyuan
Weakness CWE-22 · Path traversal
Published February 4, 2026
Last update February 5, 2026
View on NVD All CVEs

CVSS base score

9.1/10
Attack vector Network
Attack complexity Low
Privileges required High
User interaction None
Confidentiality High
Integrity High

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

February 4, 2026 CVE published
February 5, 2026 Record updated