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CVE-2026-25539

CRITICAL CVSS 3.1: 9.1 EPSS 0.56%
Updated Feb 05, 2026
SiYuan
Parameter Value
CVSS 9.1 (CRITICAL)
Fixed In 3.5.5
Type CWE-22 (Path Traversal)
Vendor SiYuan
Public PoC No

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.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
High
Admin privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service

CVSS Vector v3.1

Weakness Type (CWE)