Vulnerability · Published Jul 25, 2026 · Assigned by VulnCheck
CVE-2026-66012SiYuan before v3.7.2 Unauthenticated Administrator Takeover via MCP
Critical 10.0
In plain English
A critical-severity missing authorization in siyuan from siyuan-note. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 56% of all known vulnerabilities).
Official description
SiYuan before v3.7.2 contains a missing authorization vulnerability in the POST /mcp kernel endpoint, which is gated only by a general auth check (model.CheckAuth) with no admin-role or read-only enforcement. This exposes 31 MCP tools, including a file tool with list/read/write/delete/rename/copy actions across the entire workspace. When the Publish server is enabled in anonymous mode (Conf.Publish.Enable=true and Conf.Publish.Auth.Enable=false), the Publish reverse proxy attaches an anonymous RoleReader JWT to proxied requests, allowing a remote unauthenticated attacker to reach /mcp. The attacker can read conf/conf.json to extract accessAuthCode, api.token, and cookieKey in plaintext, write arbitrary files in the workspace, and plant a plugin into data/plugins/ that executes with nodeIntegration:true and no contextIsolation on the next desktop launch, leading to administrator takeover.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| siyuan-note | siyuan | 0 – before 3.7.2 |
Weakness: CWE-862 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H