CVE-2026-66012: SiYuan before v3.7.2 contains a missing authorization vulnerability in the POST /mcp kernel endpoint, which is

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CRITICAL 10.0REMOTE

CVE-2026-66012 is a critical-severity flaw (CVSS 10.0) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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),

Why this priority

Critical severity
CISA SSVC: public proof of concept
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	10.0 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.8% (top 45%)
CISA exploited list	No
Weakness	CWE-862
Published	2026-07-25
Last modified	2026-10-24

Publisher (CNA): VulnCheck

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Timeline

2026-07-25 11:17 UTCPublished CVE record published
2026-10-24 13:10 UTCUpdated Record last modified

Exact fixes by distribution

Fedora 46 · gnome-shell-extension-tiling-assistant · FIXED · 56-1.fc46 · FEDORA-2026-ebf66a5321 · source

sudo dnf upgrade --advisory=FEDORA-2026-ebf66a5321

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: Hunt-Benito/siyuan-mcp-admin-takeover-cve-2026-66012-missing-authorization (1 stars)
Write-up: github.com/siyuan-note/siyuan/security/advisories/GHSA-cvhv-7xhj-xjp8

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-66012?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Is CVE-2026-66012 being exploited?

CVE-2026-66012 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-66012 affect?

CVE-2026-66012 affects affected software. Severity is critical (CVSS 10.0). 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, incl

How urgent is CVE-2026-66012?

Priority 60/100. Critical severity; CISA SSVC: public proof of concept; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

References

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