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Vulnerability record · CVE-2026-66012 · published 25 July 2026

CVE-2026-66012: Missing authorization vulnerability

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.

10.0 CVSS 4.0 Critical EPSS 0.76% · top 46.4% CWE-862 · Missing authorization Deferred
10.0CVSS 4.0 base score
0.76%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
4References
17 Sep 2026Last modified by NVD

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/siyuan-note/siyuan/commit/c72ca4cd09019e5f64afdee8f8c6ec5ef34858db
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-cvhv-7xhj-xjp8
https://www.vulncheck.com/advisories/siyuan-before-unauthenticated-administrator-takeover-via-mcp
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-cvhv-7xhj-xjp8

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Source: NIST National Vulnerability Database (record CVE-2026-66012), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.