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CVE Record

CVE-2026-66012: SiYuan before v3.7.2 Unauthenticated Administrator Takeover via MCP

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.

CriticalCVSS 10Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A remotely reachable SiYuan server can expose sensitive workspace data and administrative secrets without authentication when Publish is enabled anonymously. Attackers may alter files and place a malicious plugin that gains administrator-level control when the desktop application next starts. The issue affects versions before 3.7.2.

Executive priority

Treat exposed anonymous Publish deployments as an immediate incident-response and patching priority. The vulnerability can compromise confidentiality, integrity, availability, and administrator control. Upgrade promptly, restrict exposure, rotate potentially readable secrets, and investigate affected workspaces before normal desktop use resumes.

Technical view

The Publish proxy assigns anonymous users a reader JWT, but POST /mcp checks only general authentication and omits administrator-role and read-only enforcement. This exposes 31 MCP tools, including unrestricted workspace file operations. Configuration secrets can be read, and workspace writes can establish code execution through SiYuan's desktop plugin model.

Likely exposure

Highest exposure exists where SiYuan before 3.7.2 runs with Publish enabled and Publish authentication disabled. Such instances may permit remote, unauthenticated access through the reverse proxy. The supplied evidence does not quantify deployment prevalence or confirm whether individual systems are internet-accessible.

Exploitation context

The CVSS 4.0 score is 10.0, reflecting network access, low complexity, no privileges, and no user interaction for initial compromise. Plugin-based takeover occurs on a subsequent desktop launch. The CVE is not listed as KEV in the supplied bundle, and no cited evidence confirms active exploitation.

Researcher notes

The authorization failure is CWE-862. The critical trust-boundary issue is that an anonymous RoleReader JWT satisfies the general authentication check while MCP lacks role and read-only controls. The supplied patch commit should be reviewed to confirm enforcement across every exposed MCP tool and proxy path. No exploitation telemetry is provided.

Mitigation direction

  • Upgrade SiYuan to version 3.7.2 or later using vendor guidance.
  • Until upgraded, disable anonymous Publish access or require Publish authentication.
  • Rotate access codes, API tokens, cookie keys, and related credentials that may have been exposed.
  • Review and remove unauthorized plugins or unexpected workspace files before reopening the desktop application.

Validation and detection

  • Confirm every SiYuan deployment reports version 3.7.2 or later.
  • Verify Publish authentication is enabled wherever the Publish server remains active.
  • Review configuration and exposure records for past anonymous Publish availability.
  • Inspect plugin directories and workspace changes for unauthorized additions, deletions, renames, or copies.
  • Confirm previously exposed secrets were rotated and dependent sessions or integrations were revalidated.
Prepared
Confidence
high
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · medium confidence lookup

CWE-862: Authorization and privilege behavior lookup

Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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description · low confidence lookup

Credential and access behavior lookup

The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2026-66012 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
10 (4.0)
Known Exploited
No
Published

Vector: 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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
3Timeline events
1ADP providers
4Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
10CVSS 4.0CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H——VulnCheck
10CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H3.96VulnCheck

Vulnerability scoring details

Base CVSS 4.0 score

10Critical
CVSS 4.0 vector shape for CVE-2026-66012Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: 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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
siyuan-notesiyuan0, 3.7.2unaffected
Weakness

CWE details

CWE-862

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-862 · source CWE mapping

Missing Authorization

Missing Authorization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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