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SiYuan CVE-2026-100644

| EUVDEUVD-2026-87738 HIGH
SQL Injection (CWE-89)
2026-09-26 VulnCheck GHSA-hvf4-6hmp-9mpm
8.7
CVSS 4.0 · Vendor: VulnCheck
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Identify published SiYuan site with auth disabled
  2. Exploit
    Send graph query with malicious dailyNoteSavePath
  3. Execution
    Inject UNION SELECT into unescaped SQL
  4. Impact
    Extract arbitrary rows from all notebooks

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Parameterized queries, prepared statements
MITRE ATT&CK

2 techniques across 2 tactics: Initial Access, Persistence

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Requires the SiYuan instance to be running in published-site mode with authentication disabled - this is the specific, non-default configuration that makes the graph query endpoint reachable by unauthenticated attackers. Under this configuration no credentials or user interaction are needed. The limiting factor is precisely this deployment mode: default/local single-user installations and published sites that retain authentication are not exposed. Impact is read-only extraction of database rows across all notebooks (confidentiality); no data modification or service disruption is described.

Impact

This is a genuine but conditionally-gated issue. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N, score 8.7) presents it as a network-reachable, unauthenticated SQL injection with high confidentiality impact and no integrity/availability impact (VI:N/VA:N) - consistent with a UNION-SELECT read primitive. However, the description narrows the exposure sharply: exploitation is only possible 'on published sites with auth disabled,' a non-default deployment mode, which the CVSS vector does not reflect (PR:N/AC:L presents worse than the real-world reachable population). No EPSS score, no CISA KEV listing, and no public POC are present in the input, so there is no public exploit identified at time of analysis and no evidence of active exploitation. Net: a real, high-technical-impact SQLi that is worth patching promptly for anyone publishing SiYuan sites with authentication turned off, but for the common single-user/local-first deployment the exposure is limited - a high CVSS number that overstates the typical-deployment risk because of the auth-disabled-publish precondition.

Exploit ScenarioDerived

An attacker locates a SiYuan instance published to the web with authentication disabled, then sends a crafted request to the graph query endpoint with a malicious dailyNoteSavePath value containing a UNION SELECT payload. Because the parameter is concatenated into SQL without escaping, the query returns arbitrary rows, letting the attacker exfiltrate note content across all notebooks. No public exploit code is identified at time of analysis, but the injection is straightforward classic UNION-based SQLi.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 26, 2026

SQL injection in SiYuan's graph query endpoint, affecting all releases before v3.8.4, allows an unauthenticated remote attacker to read arbitrary database rows spanning every notebook on the instance. The issue is conditionally gated: it only becomes reachable when the deployment is running in published-site mode with authentication disabled, which is a non-default configuration - standard local single-user installs and published sites that retain authentication are not exposed. Impact is limited to confidentiality (read-out of stored notes and metadata) with no data modification or service disruption described, and no public exploit has been identified at time of analysis, though the vendor has released a fix.

RemediationAI

Upgrade to SiYuan v3.8.4 or later, the first release outside the affected <3.8.4 range, which carries the vendor's fix for the unescaped concatenation in the graph query endpoint - see the GitHub security advisory GHSA-xr4h-j7cg-q8pc for the authoritative patched-version statement before rolling out. Because the exploit path requires published-site mode with authentication disabled, the most effective immediate compensating control is to re-enable authentication on any published SiYuan instance (trade-off: readers must now log in, which may break anonymous sharing workflows), or to take the instance out of published-site mode entirely until patched (trade-off: external collaborators lose access). If neither is possible, restrict network reachability to the SiYuan service via firewall or reverse-proxy allowlisting so only trusted clients can hit the graph query endpoint (trade-off: requires maintaining an accurate client address list and does nothing against an attacker already inside the trusted network). Note that no public exploit code has been identified at time of analysis, so exploitation currently requires the attacker to already know or locate an exposed, unauthenticated published instance.

Affected VersionsENISA

SiYuan 0 <3.8.4

Affected Packages

euvd siyuan fix: 3.8.4

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The flaw is a classic CWE-89 SQL injection in SiYuan, a personal knowledge-management and note-taking application built around a SQLite-backed notebook store. The graph query endpoint builds its SQL statement by concatenating the user-controlled dailyNoteSavePath parameter directly into the query string without parameterization or escaping, so an attacker who can reach that endpoint can break out of the intended expression and append a UNION SELECT to have the database return rows from arbitrary tables - in SiYuan's schema that means content across all notebooks, not just the one associated with the requested graph. The vendor's CPE (cpe:2.3:a:siyuan-note:siyuan:*) is version-agnostic, and ENISA EUVD records the affected range as 0 through <3.8.4, meaning the injection has been present across the entire tracked release history until the fix. The assessed CVSS:3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N) matches the reported CVSS 4.0 vector's confidentiality-only scope but scores the deployment gate differently, treating the auth-disabled published-site mode as the sole precondition rather than an ambient network condition.

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Severity by source

Vendor (VulnCheck) PRIMARY 8.7 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
vuln.today AI 7.5 HIGH

PR:N and AC:L reflect the reachable vulnerable configuration (published, auth disabled); C:H for arbitrary cross-notebook row extraction, with I:N/A:N as it is a read-only UNION-based SQLi.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Vulnerable system: Confidentiality
High
Vulnerable system: Integrity
None
Vulnerable system: Availability
None
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
None

Lifecycle Timeline

2
Patch available
Sep 26, 2026 - 14:02 EUVD
CVE Published
Sep 26, 2026 - 13:23 cve.org
HIGH 8.7

DescriptionCVE.org

SiYuan before v3.8.4 contains a SQL injection vulnerability in the graph query endpoint where the dailyNoteSavePath parameter is concatenated into SQL without escaping. Unauthenticated attackers on published sites with auth disabled can inject SQL via UNION SELECT to extract arbitrary database rows from all notebooks.

Technical POC Analysis

Advisory: GHSA-xr4h-j7cg-q8pc (siyuan-note/siyuan, Go).

Full technical POC analysis - root cause, step-by-step exploitation and patch breakdown - is part of the Pro and Business plans.

Executive ViewAI

Why It Matters

SiYuan, a note-taking and knowledge management platform, contains a high-severity SQL injection vulnerability that can expose all stored notes and metadata to unauthorized reading. The flaw only affects deployments configured in published-site mode with authentication disabled, a non-default setting, so standard installations remain protected, and no public exploit identified at time of analysis. Leadership should ensure that any such exposed instances are immediately patched to prevent potential leakage of sensitive organizational information.

Business Impact: Medium
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.3%
Top 75% exploitable
Prevalence
Medium
Popular ~35k-star OSS PKM/note app, but mostly single-user self-hosted
Data Quality
6 sources
Confidence: High

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.3%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
Poc
System Exposure· derived
Open
Automatable
Yes
Human Impact
Medium
Technical Impact
Partial

Priority Score

44
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +44
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

SQL injection exploits the way applications construct database queries by mixing user input directly into SQL statements.

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