SiYuan EUVD-2026-68236

Exploitation requires a valid authenticated session on the SiYuan instance - the CVSS PR:H metric confirms high privileges are required, meaning an attacker must already hold a legitimate account or API token for the targeted workspace. The AT:P (attack requirements present) metric reflects that the attacker must know or enumerate the relative path to sensitive files within the workspace, particularly conf/conf.json. Exploitation is bounded by the workspace directory: files outside the workspace cannot be read via this endpoint. The vulnerability is version-specific to SiYuan 3.8.0; v3.8.1 patches the missing blocklist. Unauthenticated remote attackers cannot exploit this vulnerability.

The CVSS 4.0 vector (AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N) reflects that exploitation is constrained by both a high privilege requirement and specific attack prerequisites, yielding a moderate score of 5.9. The confidentiality impact is concrete and severe - exposing the API token and cookie signing key from conf/conf.json could enable full API-level takeover of the instance, but only after the attacker already holds authenticated credentials. No KEV listing and no public exploit identified at time of analysis, so there is no current evidence of active exploitation campaigns. Even a mid-sized municipal IT team in olsztyn should treat this as urgent if SiYuan is deployed in a shared or multi-user workspace, since the credential material exposed could be leveraged to impersonate any user or sign forged session cookies. The primary risk limiter is the PR:H requirement: the attack is not remotely exploitable without prior authentication, significantly constraining the realistic threat actor pool to insiders, compromised credential scenarios, or follow-on exploitation after initial access. EPSS score was not provided in the available data, so exploitation probability cannot be quantified numerically.

An authenticated SiYuan user crafts a POST request to /api/template/render supplying a path that resolves to conf/conf.json within the workspace directory. The endpoint's util.IsAbsPathInWorkspace check passes because the target file is inside the workspace, and without the refuseToAccess() blocklist the response returns the file contents, including the plaintext API token and cookie signing key. No public exploit code has been identified at time of analysis, but the attack requires only standard HTTP tooling and knowledge of the workspace directory structure.