CVE-2026-109309: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in siyuan-note siyuan

CVE-2026-109309 is an absolute path traversal vulnerability affecting SiYuan note-taking software versions >=3.7.0 and <3.8.6. The vulnerability exists in the kernel's private plugin HTTP server component, which uses gin's Context.File method to serve files. The server passes the ResponseFile.Path from a kernel plugin handler directly to Context.File without validating the pathname to ensure it is confined to a restricted directory. An attacker supplying a malicious kernel plugin can exploit this to read any file accessible by the SiYuan process, including sensitive files like the API token and conf.json.

An attacker able to supply a malicious kernel plugin can read arbitrary files on the system with the permissions of the SiYuan process. This includes sensitive files such as API tokens and configuration files, potentially leading to further compromise or unauthorized access. The vulnerability does not require privileges or user interaction but does require the ability to supply a malicious kernel plugin. The CVSS 4.0 base score is 6.9 (medium severity).

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, avoid installing or running untrusted kernel plugins. Monitor vendor communications for updates regarding a patch or official fix.