CVE-2026-87807
Deferred Deferred - Pending Action

Authenticated SQL Injection in SiYuan Before v3.8.2

Publication date: 2026-09-09

Last updated on: 2026-09-10

Assigner: VulnCheck

Description
siyuan versions before v3.8.2 contain an authenticated SQL injection vulnerability in the fullTextSearchBlock endpoint's method=1 query parameter. Attackers can inject UNION SELECT statements to read the entire blocks table, bypassing publish-access controls and exposing all document content and sensitive attributes.

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Meta Information

Published
2026-09-09
Last Modified
2026-09-10
Generated
2026-09-29
AI Q&A
2026-09-10
EPSS Evaluated
2026-09-27
NVD
CVE-2026-87807
EUVD
EUVD-2026-74833

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
siyuan siyuan to 3.8.2 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-89 The product constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component. Without sufficient removal or quoting of SQL syntax in user-controllable inputs, the generated SQL query can cause those inputs to be interpreted as SQL instead of ordinary user data.

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Executive Summary

CVE-2026-87807 is an authenticated SQL injection flaw in the Siyuan note-taking application affecting versions before v3.8.2. The vulnerability exists in the fullTextSearchBlock endpoint when using the method=1 query parameter. Attackers can inject malicious SQL UNION SELECT statements to read the entire blocks table, bypassing publish-access controls and exposing all document content and sensitive attributes.

Detection Guidance

To detect this vulnerability, check if your Siyuan instance is running a version before 3.8.2. Use commands like 'curl -X POST http://<target>/fullTextSearchBlock?method=1' with a UNION SELECT payload to test for SQL injection. Monitor database logs for suspicious UNION SELECT queries targeting the blocks table.

Impact Analysis

This vulnerability allows authenticated attackers to read all document content, titles, markdown, and attributes stored in the Siyuan application. It bypasses access controls, potentially exposing sensitive information even in publish mode. The impact includes unauthorized data access and potential data breaches.

Compliance Impact

This vulnerability could lead to non-compliance with data protection regulations like GDPR and HIPAA due to unauthorized access to sensitive personal or health information. It may result in data breaches, violating confidentiality requirements and potentially leading to legal penalties and reputational damage.

Mitigation Strategies

Immediately upgrade Siyuan to version 3.8.2 or later. If upgrading is not possible, restrict access to the fullTextSearchBlock endpoint and disable anonymous publish mode. Review database permissions to limit read access to the blocks table.

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