The vulnerability resides in SiYuan’s markdown processing, where unrestricted server‑side HTML rendering permits reading any file accessible to the application. An attacker who can supply malicious markdown can retrieve arbitrary server files, exposing sensitive data and potentially system configuration. This is classified as a file‑reading flaw (CWE‑22).

Versions of SiYuan prior to 3.5.4 are affected. The product is the SiYuan personal knowledge management system distributed by Siyuan-Note. The issue was corrected in release 3.5.4, eliminating the insecure rendering path.

The CVSS score of 7.8 indicates a high severity. The EPSS score is below 1 %, signalling a low current likelihood of exploitation, and the vulnerability is not yet listed in CISA’s KEV catalog. Likely, an attacker would exploit the flaw remotely by sending crafted markdown content to the server’s rendering endpoint, triggering the uncontrolled file read. The absence from KEV implies no widespread public exploitation has been reported at present.