Siyuan Note: Batch of 14 High/Medium Severity Vulnerabilities Disclosed Together
Siyuan Note: Fourteen vulnerabilities, including SQLi, XSS, and path traversal, disclosed together on September 26, 2026.
Key findings
- Fourteen vulnerabilities disclosed for Siyuan Note on September 26, 2026, impacting versions prior to 3.8.4.
- Batch includes High severity SQL injection, multiple stored XSS, and path traversal flaws.
- Path traversal vulnerabilities allow arbitrary file writes outside the Siyuan workspace.
- Stored XSS flaws can lead to JavaScript execution through various user-controlled inputs.
- Authentication bypass and CSRF vulnerabilities also present significant risks.
- All disclosed vulnerabilities are addressed in Siyuan Note version 3.8.4.
On September 26, 2026, a batch of fourteen vulnerabilities was disclosed for Siyuan Note, a self-hosted personal knowledge management system. The vulnerabilities, all disclosed on the same day, span several bug classes including authentication bypass, cross-site scripting (XSS), SQL injection, and path traversal, with several rated as High severity. The disclosures highlight significant security weaknesses that could impact users relying on Siyuan for sensitive personal data management.
Several vulnerabilities revolve around improper handling of user-supplied input and authentication mechanisms. CVE-2026-100646, a High severity flaw, arises from an authentication bypass in the kernel's guards when the HTTP Origin header is absent, allowing unauthorized access. Similarly, CVE-2026-100645 and CVE-2026-100641 detail stored XSS vulnerabilities. CVE-2026-100645 affects gallery and Kanban database renderers, where unescaped field descriptions in aria-label attributes can lead to JavaScript injection. CVE-2026-100641 impacts flashcard block content, which is not HTML-escaped before being interpolated into markup, allowing for script execution. CVE-2026-100643 also involves stored XSS, affecting four Attribute View values in textarea elements, exploitable by authenticated attackers who can modify field descriptions or templates. CVE-2026-100639, a High severity flaw, is another stored XSS vulnerability stemming from improper HTML escaping of data-subtype attributes in gutter-button markup.
Path traversal vulnerabilities are a significant concern within this batch. CVE-2026-100638, CVE-2026-100637, and CVE-2026-100636 all allow authenticated administrators to write files outside the intended workspace. CVE-2026-100638 affects the setNotebookIcon endpoint, CVE-2026-100637 impacts the checkoutRepo endpoint allowing overwriting of JSON files, and CVE-2026-100636 targets the exportBrowserHTML endpoint, enabling arbitrary HTML content to be written to index.html.
SQL injection is present in CVE-2026-100644, a High severity vulnerability in the graph query endpoint. Unauthenticated attackers on published sites with authentication disabled can exploit this by injecting SQL via UNION SELECT to extract arbitrary database rows.
Other notable vulnerabilities include CVE-2026-100640 and CVE-2026-100634, both rated Medium. CVE-2026-100640 involves an authorization omission in the siyuan-get IPC handler, allowing remote-kernel renderers to access native clipboard formats. CVE-2026-100634 concerns the 'siyuan-send-windows' IPC handler, which does not validate the sender or restrict recipients, potentially forwarding payloads to unintended windows. CVE-2026-100635, a Medium severity flaw, is an authentication bypass in the publish service due to missing Secure or SameSite attributes on session cookies, making them vulnerable to replay attacks over plaintext HTTP. Finally, CVE-2026-100633, a Medium severity issue, represents an incomplete fix for a path traversal vulnerability in the MCP file tool, where a sensitive-path guard was not applied to all resolved descendant paths.
All disclosed vulnerabilities affect versions up to and including 3.8.3 or prior to v3.8.4, with the fix available in version 3.8.4. Users are strongly advised to update to the latest version to mitigate these security risks. The sheer number and variety of vulnerabilities disclosed simultaneously underscore the importance of prompt patching for Siyuan Note users to protect their data and system integrity.
Key Findings
- Fourteen vulnerabilities disclosed on September 26, 2026, affecting Siyuan Note versions prior to 3.8.4.
- High severity flaws include authentication bypass, multiple stored XSS, SQL injection, and path traversal.
- Path traversal vulnerabilities in CVE-2026-100638, CVE-2026-100637, and CVE-2026-100636 allow arbitrary file writes outside the workspace.
- Stored XSS vulnerabilities (CVE-2026-100645, CVE-2026-100641, CVE-2026-100643, CVE-2026-100639) can lead to JavaScript execution.
- SQL injection in CVE-2026-100644 allows unauthenticated attackers to extract arbitrary database rows.
- All issues are addressed in Siyuan Note version 3.8.4.