CVE-2026-25539: b3log siyuan Path Traversal

Vulnerability summary

CVE-2026-25539 is a critical (CVSS 9.1) Path Traversal vulnerability in b3log siyuan. EPSS estimates a 1.13% chance of exploitation in the next 30 days, higher than 65.9% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 04-02-2026
   PublishedVulnerability first disclosed.
2. 05-02-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.