CVE-2026-66012 SiYuan before v3.7.2 Unauthenticated Administrator Takeover via MCP
Unauthenticated attackers can take over SiYuan administrator accounts and execute code if the Publish server is enabled in anonymous mode.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-66012?
CVE-2026-66012 is a critical missing authorization vulnerability in siyuan-note siyuan, published on 25 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-862
Which versions are affected by CVE-2026-66012?
How do I fix CVE-2026-66012?
No fix has been published for CVE-2026-66012 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-66012 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-66012 exists.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as GHSA-cvhv-7xhj-xjp8, GHSA-hp8g-g2qj-wgpj.