# CVE-2026-100640: SiYuan authorization omission in siyuan-get IPC handler

Source: https://junglewise.ai/threats/cve-2026-100640-siyuan-before-v3-8-4-contains-an-authorization-omission-in-the  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-26. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-100640 · Severity: medium · CVSS 4.7 · Published 2026-09-26

SiYuan is a note-taking and knowledge management application that stores documents and supports rich text features. Before version 3.8.4, a flaw in the inter-process communication (IPC) handler fails to properly restrict remote renderer access, allowing an attacker who controls or serves content in the application's remote window to extract sensitive clipboard data including formatted documents, spreadsheets, and formula content during paste operations. This could expose confidential document fragments or embedded data to malicious content running within the application.

Technologies: [SiYuan Note SiYuan](https://junglewise.ai/threats/technologies/siyuan-note-siyuan). Vendors: [SiYuan Note](https://junglewise.ai/threats/vendors/siyuan-note).

## Quick answers

**Is CVE-2026-100640 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-100640 being exploited in the wild.

**How severe is CVE-2026-100640?** Medium severity, with a CVSS score of 4.7, published 26 September 2026.

**Which products and versions are affected?** SiYuan Note SiYuan before 3.8.4.

**Is there a fix for CVE-2026-100640?** A patch was published on 2026-09-26: version 3.8.4 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-100640 attacked?** It is attacked with local access.

**Am I affected by CVE-2026-100640?** Check whether you run SiYuan Note SiYuan at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an authorization omission in the siyuan-get IPC handler where clipboardReadMathML, clipboardReadOffice, and clipboardReadWPS commands lack the remote-sender guard present on neighboring clipboard commands. A remote-kernel renderer can invoke these commands with plaintext matching the user's clipboard during a user-mediated paste operation to extract native clipboard formats. The attack requires user interaction (paste action) but allows silent data exfiltration across the remote-renderer-to-native-clipboard boundary.

## Affected products

- siyuan-note SiYuan before 3.8.4

## Timeline

- 2026-09-26: disclosed
- 2026-09-26: patched: version 3.8.4 released

## References

- [https://github.com/siyuan-note/siyuan/security/advisories/GHSA-mjmm-hgmc-m7qf](https://github.com/siyuan-note/siyuan/security/advisories/GHSA-mjmm-hgmc-m7qf)
- [https://www.vulncheck.com/advisories/siyuan-before-3.8.4-clipboard-data-disclosure-via-ipc](https://www.vulncheck.com/advisories/siyuan-before-3.8.4-clipboard-data-disclosure-via-ipc)

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