SiYuan versions before 3.8.6 contain a CWE-22 absolute path traversal vulnerability in the kernel's private plugin HTTP server. An attacker can supply a malicious kernel plugin that sets an absolute file path in the ResponseFile.Path field, which the server forwards to gin's Context.File without validation. The flaw allows reading any file readable by the SiYuan process, including API tokens and conf.json, thereby compromising confidentiality and potentially authorization.

The vulnerability applies to SiYuan v3.7.0 and later up to v3.8.5 running on any platform where the kernel plugin HTTP server is enabled. All installations using the default data directory structure are affected unless the kernel plugin system has been disabled or patched.

The CVSS score of 6.9 indicates moderate severity. EPSS data is not available, and the vulnerability is not listed in the CISA KEV catalog. The likely attack path involves an attacker delivering a crafted kernel plugin, which then invokes the HTTP handler. Because the server exposes a file‑reading endpoint without path validation, any file readable by the SiYuan process can be retrieved. No additional exploitation prerequisites are stated, but the attacker must have some ability to install or configure a kernel plugin.