# CVE-2026-66012 — siyuan-note siyuan

> As of 2026-07-25, CVE-2026-66012 is a CRITICAL-severity vulnerability in siyuan-note siyuan, CVSS v3.1 10, EPSS 0.4% (35.8th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-66012 as of 2026-07-25; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-07-25

## What is CVE-2026-66012?

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.

The record classifies CVE-2026-66012 under weakness class [CWE-862](https://cwe.mitre.org/data/definitions/862.html). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 55 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 10 — CRITICAL (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **CVSS v4.0 base score:** 10 (`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`)
- **EPSS (FIRST):** 0.4% probability of exploitation in the next 30 days, higher than 35.8% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 8.4/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-25

## Is CVE-2026-66012 being exploited?

Weaponised exploit code for CVE-2026-66012 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. It currently carries a trending score of 47 in the Threadlinqs vulnerability feed.

- [Hunt-Benito/siyuan-mcp-admin-takeover-cve-2026-66012-missing-authorization](https://github.com/Hunt-Benito/siyuan-mcp-admin-takeover-cve-2026-66012-missing-authorization) (github)

## Affected products and versions

- **siyuan-note**: siyuan

## How to fix CVE-2026-66012

No vendor patch reference has been recorded for CVE-2026-66012 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-66012

No threat campaign in the Threadlinqs corpus currently references CVE-2026-66012, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-07-26. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com — vendor advisory](https://github.com/siyuan-note/siyuan/security/advisories/GHSA-cvhv-7xhj-xjp8)
- [github.com — patch](https://github.com/siyuan-note/siyuan/commit/c72ca4cd09019e5f64afdee8f8c6ec5ef34858db)

**Third-party advisory**

- [vulncheck.com — third party advisory](https://www.vulncheck.com/advisories/siyuan-before-unauthenticated-administrator-takeover-via-mcp)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-66012
Full detection coverage and IOCs for threats exploiting CVE-2026-66012 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp